chore(deps): update actions/checkout action to v6 (#619)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/checkout](https://redirect.github.com/actions/checkout) |
action | major | `v5` -> `v6` |

---

### Release Notes

<details>
<summary>actions/checkout (actions/checkout)</summary>

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

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

</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.

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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

---

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View the [repository job
log](https://developer.mend.io/github/bazel-contrib/toolchains_llvm).

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.github/workflows/release.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Prepare release
         run: .github/workflows/release_prep.sh > release_notes.txt
       - name: Release

.github/workflows/tests.yml

@@ -20,7 +20,7 @@ jobs:
       contents: read # For repo checkout
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Trunk Check
         uses: trunk-io/trunk-action@v1
   test:
@@ -33,7 +33,7 @@ jobs:
         bzlmod: [true, false]
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - if: startsWith(matrix.os, 'ubuntu')
         run: tests/scripts/ubuntu_install_libtinfo.sh
       - run: sudo rm -rf /usr/share/dotnet /usr/local/lib/android
@@ -51,7 +51,7 @@ jobs:
         bzlmod: [true, false]
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Test
         env:
           USE_BAZEL_VERSION: ${{ matrix.bazel_version }}
@@ -66,7 +66,7 @@ jobs:
         bzlmod: [true, false]
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - if: startsWith(matrix.os, 'ubuntu')
         run: tests/scripts/ubuntu_install_libtinfo.sh
       - name: Test
@@ -92,7 +92,7 @@ jobs:
         bzlmod: [true, false]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - run: sudo rm -rf /usr/share/dotnet /usr/local/lib/android
       - name: Test
         env:
@@ -105,7 +105,7 @@ jobs:
         bzlmod: [true, false]
     runs-on: macos-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Test
         env:
           USE_BZLMOD: ${{ matrix.bzlmod }}
@@ -117,7 +117,7 @@ jobs:
         bzlmod: [true, false]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - run: tests/scripts/ubuntu_install_libtinfo.sh
       - name: Test
         env:
@@ -130,7 +130,7 @@ jobs:
         bzlmod: [true, false]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - run: tests/scripts/ubuntu_install_libtinfo.sh
       - name: Download and Extract LLVM distribution
         # The downloaded version here must match version specified as '-v' arg to run_tests.sh below.