github actions: code coverage job is non-blocking

Author: dg

.github/workflows/tests.yml

@@ -47,6 +47,7 @@ jobs:
     code_coverage:
         name: Code Coverage
         runs-on: ubuntu-latest
+        continue-on-error: true
         steps:
             - uses: KeisukeYamashita/memcached-actions@v1
             - uses: actions/checkout@v4