.github/workflows: temporary use macOS-15

Since WillAbides/setup-go-faster failed with macOS-latest.

Author: cuonglm

.github/workflows/ci.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: ["windows-latest", "ubuntu-latest", "macOS-latest"]
+        os: ["windows-latest", "ubuntu-latest", "macOS-15"]
         go: ["1.24.x"]
     runs-on: ${{ matrix.os }}
     steps: