ci: enable code coverage job in default ci

Information about test code coverage is useful on code review.
This patch enables code coverage job in default ci.

NO_CHANGELOG=not a user-visible change
NO_DOC=not a user-visible change
NO_TEST=ci

.github/workflows/coverage.yml

@@ -34,10 +34,11 @@ concurrency:
 jobs:
   coverage:
     # Run on push to the 'master' and release branches of tarantool/tarantool
-    # or on pull request if the 'full-ci' label is set.
+    # or on pull request if the 'notest' label is not set.
     if: github.repository == 'tarantool/tarantool' &&
         ( github.event_name != 'pull_request' ||
-          contains(github.event.pull_request.labels.*.name, 'full-ci') )
+          ( github.event_name == 'pull_request' &&
+            !contains(github.event.pull_request.labels.*.name, 'notest') ) )
 
     runs-on: ubuntu-20.04-self-hosted