chore: upgrade to macos-15 runners (#2259)

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## What this PR does / why we need it:

`mac-13` runners will be deprecated.

## Does this PR introduce a user-facing change?
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If no, just write "no" in the block below.
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```
no
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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Update CI matrices to use macos-15 instead of macos-13 in deployment
and preview workflows.
> 
> - **CI Workflows**:
> - Update OS matrix in `.github/workflows/ci-sync-deployment.yml` and
`.github/workflows/ci-sync-preview.yml`:
>     - Replace `macos-ventura`/`macos-13` with `macos-15`.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
e319475. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: snakster

.github/workflows/ci-sync-deployment.yml

@@ -26,8 +26,8 @@ jobs:
         os:
           - name: ubuntu
             value: "blacksmith-4vcpu-ubuntu-2404"
-          - name: macos-ventura
-            value: "macos-13"
+          - name: macos-15
+            value: "macos-15"
 
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # pin@v4

.github/workflows/ci-sync-preview.yml

@@ -23,8 +23,8 @@ jobs:
         os:
           - name: ubuntu
             value: "blacksmith-4vcpu-ubuntu-2404"
-          - name: macos-ventura
-            value: "macos-13"
+          - name: macos-15
+            value: "macos-15"
 
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # pin@v4