Fix test-backend — remove redundant CLI path arg conflicting with roots

The jest.roots config in package.json already restricts to backend/__tests__
and testPathIgnorePatterns excludes integration tests. The CLI path arg
was being interpreted as an additional ignore pattern, causing 0 matches.

.gitlab-ci.yml

@@ -100,7 +100,7 @@ test-backend:
     policy: pull
   script:
     - test -d node_modules || npm ci
-    - ./node_modules/.bin/jest --ci --forceExit --testPathIgnorePatterns='integration' backend/__tests__/
+    - ./node_modules/.bin/jest --ci --forceExit
   timeout: 5 minutes
   needs:
     - install-backend