ci: Re-enable Coverage

'contents' appears to be required for the coverage action. I've enabled
this on a couple of other repos and this appears to work.

.github/workflows/coverage.yml

@@ -4,11 +4,11 @@ on:
   - pull_request
 
 permissions:
+  contents: read
   pull-requests: write
 
 jobs:
   coverage:
-    if: false
     runs-on: ubuntu-latest
     defaults:
       run: