Fix update-tests-metadata job due to bundler requirement

The rails gem requires bundler >= 1.3.0. Since Ruby v2.7.2 comes with
bundler v2, we need to install v1.17.3 to meet this requirement.

.gitlab/ci/test-metadata.gitlab-ci.yml

@@ -38,6 +38,6 @@ update-tests-metadata:
     - rspec-ee integration pg11 geo
     - rspec-ee system pg11 geo
   script:
-    - run_timed_command "retry gem install fog-aws mime-types activesupport rspec_profiling postgres-copy --no-document"
+    - run_timed_command "retry gem install bundler:1.17.3 fog-aws mime-types activesupport rspec_profiling postgres-copy --no-document"
     - source ./scripts/rspec_helpers.sh
     - update_tests_metadata