CI: minor clean-up

1. GitLab does not seem to generate the exposed artifact view for failed pipelines and the patch artifact is uploaded for failed pipelines only. Therefore, the respective expose_as entries are removed from the CI configuration file.
2. apk and pre-commit caches are now cleaned/verified separately.

.gitlab-ci.yml

@@ -33,11 +33,11 @@ workflow:
   before_script:
     - mkdir -p "${APK_CACHE_DIR}"
     - apk --cache-dir "${APK_CACHE_DIR}" --update-cache add git pre-commit
+    - apk --cache-dir "${APK_CACHE_DIR}" cache clean
     - |
-      # Clean up cache
+      # Verify pre-commit cache
       (
         set -o pipefail
-        apk --cache-dir "${APK_CACHE_DIR}" cache clean
         python3 --version | diff - "${PRE_COMMIT_HOME}/python_version.txt" 2>/dev/null || {
           rm -rf "${PRE_COMMIT_HOME}"
           mkdir -p "${PRE_COMMIT_HOME}"
@@ -104,7 +104,6 @@ Check style:
   artifacts:
     paths:
       - ${STYLE_PATCH}
-    expose_as: 'Style Patch'
     when: on_failure
 
   rules: