Switch the mac workflow to macos-13, since macos-12 is no longer available.

Author: Sedeniono

.github/workflows/test_clang_mac.yml

@@ -17,7 +17,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [macos-12] # macos-12 is x64
+        os: [macos-13] # macos-13 is x64
 
         # Note: No clang version variation since the macOS runners to not have versioned executables (e.g. clang++-13).
         cpp_version: [c++17, c++20]
@@ -26,7 +26,7 @@ jobs:
         include:
           # Also include a few variations with disabled UB tricks (not for all to limit resource consumption).
           # Especially include some on arm64 where the UB tricks are not supported by tiny::optional.
-          - os: macos-12 # macos-12 is x64
+          - os: macos-13 # macos-13 is x64
             cpp_version: c++20
             buildmode: -DTINY_OPTIONAL_USE_SEPARATE_BOOL_INSTEAD_OF_UB_TRICKS
           - os: macos-14 # macos-14 is arm64