ci: simplify test job name

Remove matrix variable interpolation from job name as GitHub Actions
doesn't support it at the job level. The matrix strategy still runs
tests across all Node versions and OS combinations.

Author: jdalton

.github/workflows/ci.yml

@@ -80,7 +80,7 @@ jobs:
 
   # Test matrix - reuses build artifacts
   test:
-    name: Test (Node ${{ matrix.node }} / ${{ matrix.os }})
+    name: Test
     needs: [lint, build]
     runs-on: ${{ matrix.os }}
     timeout-minutes: 15