CI: Remove 'check_release'-CI-job and 'check_release.py'

This CI-job is a reminder to publish a tag,
when there is no tag for the current version-number.

This does not work well when the version-number is increased
after a release, because there will be no such tag,
until the next release has been published.

Part-of: <https://gitlab.gnome.org/World/Phosh/squeekboard/-/merge_requests/701>

.gitlab-ci.yml

@@ -113,19 +113,6 @@ test_style:
     variables:
       - $PKG_ONLY == "1"
 
-check_release:
-  stage: test
-  needs: []
-  only:
-    refs:
-      - main
-  script:
-    - apt-get -y install git python3
-    - (head -n 1 ./debian/changelog && git tag) | ./debian/check_release.py
-  except:
-    variables:
-      - $PKG_ONLY == "1"
-
 pages:
   stage: deploy
   needs: