[CI] Use x86 MacOS runner

GitHub changed `macos-latest` to be an ARM runner. Until we have MacOS
ARM wheels (OpenAssetIO/OpenAssetIO#718) we must pin to the last x86
runner version.

Signed-off-by: David Feltell <david.feltell@foundry.com>

Author: feltech

.github/workflows/test.yml

@@ -32,7 +32,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: ["windows-latest", "ubuntu-latest", "macos-latest"]
+        os: ["windows-latest", "ubuntu-latest", "macos-13"]
         python: ["3.7", "3.9", "3.10"]
     steps:
       - uses: actions/checkout@v4