chore(deps): update actions/setup-node action to v6 (#954)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/setup-node](https://redirect.github.com/actions/setup-node) |
action | major | `v4` -> `v6` |

---

### Release Notes

<details>
<summary>actions/setup-node (actions/setup-node)</summary>

###
[`v6`](https://redirect.github.com/actions/setup-node/compare/v5...v6)

[Compare
Source](https://redirect.github.com/actions/setup-node/compare/v5...v6)

###
[`v5`](https://redirect.github.com/actions/setup-node/compare/v4...v5)

[Compare
Source](https://redirect.github.com/actions/setup-node/compare/v4...v5)

</details>

---

### Configuration

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Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you
are satisfied.

♻ **Rebasing**: Whenever PR is behind base branch, or you tick the
rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update
again.

---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
this box

---

This PR was generated by [Mend Renovate](https://mend.io/renovate/).
View the [repository job
log](https://developer.mend.io/github/launchdarkly/js-core).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0MS4xNDMuMSIsInVwZGF0ZWRJblZlciI6IjQxLjE3My4xIiwidGFyZ2V0QnJhbmNoIjoibWFpbiIsImxhYmVscyI6W119-->

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Pins actions/setup-node to v6 (commit 2028fbc...) across all CI and
release workflows.
> 
> - **CI/CD**:
> - Pin `actions/setup-node` to commit
`2028fbc5c25fe9cf00d9f06a71cc4710d4507903` (v6) across
`.github/workflows/**`, including build/test jobs and `release-please`
release steps.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
73759c1. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/akamai-base.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@2028fbc5c25fe9cf00d9f06a71cc4710d4507903 # v6
       - id: shared
         name: Shared CI Steps
         uses: ./actions/ci

.github/workflows/akamai-edgekv.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@2028fbc5c25fe9cf00d9f06a71cc4710d4507903 # v6
       - id: shared
         name: Shared CI Steps
         uses: ./actions/ci

.github/workflows/akamai-edgeworker-sdk.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@2028fbc5c25fe9cf00d9f06a71cc4710d4507903 # v6
         with:
           node-version: 24.x
           registry-url: 'https://registry.npmjs.org'

.github/workflows/browser-telemetry.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@2028fbc5c25fe9cf00d9f06a71cc4710d4507903 # v6
         with:
           node-version: 24.x
           registry-url: 'https://registry.npmjs.org'

.github/workflows/browser.yml

@@ -23,7 +23,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@2028fbc5c25fe9cf00d9f06a71cc4710d4507903 # v6
         with:
           node-version: ${{ matrix.version }}
           registry-url: 'https://registry.npmjs.org'

.github/workflows/cloudflare.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@2028fbc5c25fe9cf00d9f06a71cc4710d4507903 # v6
       - id: shared
         name: Shared CI Steps
         uses: ./actions/ci

.github/workflows/combined-browser.yml

@@ -23,7 +23,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@2028fbc5c25fe9cf00d9f06a71cc4710d4507903 # v6
         with:
           node-version: ${{ matrix.version }}
           registry-url: 'https://registry.npmjs.org'

.github/workflows/common.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@2028fbc5c25fe9cf00d9f06a71cc4710d4507903 # v6
         with:
           node-version: 24.x
           registry-url: 'https://registry.npmjs.org'

.github/workflows/fastly.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@2028fbc5c25fe9cf00d9f06a71cc4710d4507903 # v6
       - id: shared
         name: Shared CI Steps
         uses: ./actions/ci

.github/workflows/jest.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@2028fbc5c25fe9cf00d9f06a71cc4710d4507903 # v6
       - id: shared
         name: Shared CI Steps
         uses: ./actions/ci