Fix: use 'yarn run test --browsers=ChromeHeadlessCI' in CI

The direct 'yarn ng test' command fails on CI in 2s. Use the package.json
'test' script instead, which already has --source-map=true, --watch=false,
and --configuration test. Add --browsers=ChromeHeadlessCI for headless mode.
Coverage (--code-coverage) is kept in test:headless for local use.

Author: milanmajchrak

.github/workflows/build.yml

@@ -112,7 +112,7 @@ jobs:
       # DSpace works because their test suite is smaller. The --code-coverage
       # flag is preserved in package.json test:headless for local use.
       - name: Run specs (unit tests)
-        run: yarn ng test --source-map=true --watch=false --configuration test --browsers=ChromeHeadlessCI
+        run: yarn run test --browsers=ChromeHeadlessCI
 
       # Upload code coverage report to artifact (for one version of Node only),
       # so that it can be shared with the 'codecov' job (see below)