Eliminate macOS 12->13 variable.

.github/workflows/ci.yml

@@ -25,7 +25,7 @@ jobs:
   mac-tests:
     name: tox -e ${{ matrix.tox-env }} ${{ matrix.pex-test-pos-args }}
     needs: org-check
-    runs-on: macos-13
+    runs-on: macos-12
     strategy:
       matrix:
         include:
@@ -51,16 +51,16 @@ jobs:
         uses: actions/cache/restore@v4
         with:
           path: ${{ env._PEX_TEST_DEV_ROOT }}/pyenv
-          key: macos-13-${{ runner.arch }}-pex-test-dev-root-pyenv-v1
+          key: macos-12-${{ runner.arch }}-pex-test-dev-root-pyenv-v1
       - name: Restore Cached Devpi Server
         id: restore-devpi-server
         uses: actions/cache/restore@v4
         with:
           path: ${{ env._PEX_TEST_DEV_ROOT }}/devpi
           # We're using a key suffix / restore-keys prefix trick here to get an updatable cache.
           # See: https://github.com/actions/cache/blob/main/tips-and-workarounds.md#update-a-cache
-          key: macos-13-${{ runner.arch }}-${{ matrix.tox-env }}-pex-test-dev-root-devpi-v1-${{ github.run_id }}
-          restore-keys: macos-13-${{ runner.arch }}-${{ matrix.tox-env }}-pex-test-dev-root-devpi-v1
+          key: macos-12-${{ runner.arch }}-${{ matrix.tox-env }}-pex-test-dev-root-devpi-v1-${{ github.run_id }}
+          restore-keys: macos-12-${{ runner.arch }}-${{ matrix.tox-env }}-pex-test-dev-root-devpi-v1
       # Some ITs need this for VCS URLs of the form git+ssh://[email protected]/...
       - name: Setup SSH Agent
         uses: webfactory/[email protected]