.github: workflows: drop macos-15-intel

Drop macos-15-intel, it's not supported anymore.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>

Author: fabiobaltieri

.github/workflows/build.yml

@@ -15,7 +15,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-22.04, macos-14, macos-15-intel, windows-2022]
+        os: [ubuntu-22.04, macos-14, windows-2022]
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout