ci: configure rules to enable dependent jbos in continuous pipeline

Apply the rules from commit ff72dbfb14 (gitlab-ci: configure rules to
enable continuous builds of staged MRs, 2020-09-30, v3.19.0-rc1~70^2~1)
and commit 71665c8cb9 (gitlab-ci: Clarify conditions enabling jobs for
continuous build of stage, 2021-05-05, v3.21.0-rc1~218^2) to dependent
jobs too.

.gitlab/rules.yml

@@ -52,6 +52,8 @@
           when: on_success
         - if: '$CMAKE_CI_JOB_NIGHTLY == "true"'
           when: never
+        - if: '$CMAKE_CI_PROJECT_CONTINUOUS_BRANCH != null && $CI_COMMIT_BRANCH != null && $CMAKE_CI_PROJECT_CONTINUOUS_BRANCH == $CI_COMMIT_BRANCH && $CMAKE_CI_JOB_CONTINUOUS == "true"'
+          when: on_success
         - if: '($CMAKE_CI_NO_MR == "true" && $CI_MERGE_REQUEST_ID)'
           when: never
         - if: '$CI_MERGE_REQUEST_ID'