ci: use free macos-15-intel runner for x64 macOS builds

Replace macos-15-large (paid) with macos-15-intel (free) for the
x86_64-apple-darwin release build target.

Author: farhan-syah

.github/workflows/release.yml

@@ -183,7 +183,7 @@ jobs:
           - runs-on: macos-latest
             target: aarch64-apple-darwin
             label: macos-arm64
-          - runs-on: macos-15-large
+          - runs-on: macos-15-intel
             target: x86_64-apple-darwin
             label: macos-x64
           - runs-on: windows-latest