CI: simplify `pages` job, remove unneeded js libs

.gitlab-ci.yml

-image: alpine:latest
-
 pages:
   stage: deploy
+  image: alpine:latest
   script:
-    - mkdir .public
-    - cp -r * .public
-    - mv .public public
+    - 'true'
   artifacts:
     paths:
       - public
-  only:
-    - master
+  rules:
+    - if: '$CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH'

public/index.html

@@ -32,11 +32,5 @@
     </p>
 
    </div>
-
-    <!-- Optional JavaScript -->
-    <!-- jQuery first, then Popper.js, then Bootstrap JS -->
-    <script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
-    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>
-    <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>
   </body>
-</html>
\ No newline at end of file
+</html>