fix: Add checkout step to coverage-report job

The coverage-report job was failing on fork PRs with:
'The current working directory is not inside a git repository'

The fgrosse/go-coverage-report action needs the repository
checked out to function properly. Added checkout step before
the coverage report action.

Fixes workflow failures on external contributor PRs.

Author: lykinsbd

.github/workflows/test.yml

@@ -58,6 +58,9 @@ jobs:
       actions: read
       pull-requests: write
     steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      
       - uses: fgrosse/go-coverage-report@v1.1.1
         with:
           coverage-artifact-name: code-coverage