CI: Use matrix.os instead of runner.os in artifact name

Fixes error `Failed to CreateArtifact: Received non-retryable error: Failed request: (409) Conflict: an artifact with this name already exists on the workflow run` on the ubuntu-24.04-arm job. Patches #3778

Author: weiji14

.github/workflows/ci_tests.yaml

@@ -177,7 +177,7 @@ jobs:
         uses: actions/[email protected]
         if: failure()
         with:
-          name: artifact-${{ runner.os }}-${{ matrix.python-version }}
+          name: artifact-${{ matrix.os }}-${{ matrix.python-version }}
           path: tmp-test-dir-with-unique-name
 
       # Upload coverage to Codecov

.github/workflows/ci_tests_dev.yaml

@@ -185,5 +185,5 @@ jobs:
         uses: actions/[email protected]
         if: ${{ failure() }}
         with:
-          name: artifact-GMT-${{ matrix.gmt_git_ref }}-${{ runner.os }}
+          name: artifact-GMT-${{ matrix.gmt_git_ref }}-${{ matrix.os }}
           path: tmp-test-dir-with-unique-name