Run GUI test when browser-ui-test version is updated

Author: GuillaumeGomez

src/ci/scripts/should-skip-this.sh

@@ -25,6 +25,7 @@ if [[ -n "${CI_ONLY_WHEN_SUBMODULES_CHANGED-}" ]]; then
     elif ! (git diff --quiet "$BASE_COMMIT" -- \
              src/test/rustdoc-gui \
              src/librustdoc \
+             src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile \
              src/tools/rustdoc-gui); then
         # There was a change in either rustdoc or in its GUI tests.
         echo "Rustdoc was updated"