Version checker (#3102)

* Updates for docker version check script:

- Do not run on a push to stable
- Check existing versions via GitHub API
- Add stable docker image tag also

* Fix regex pattern

* Check for null regex result

* Push to stable on tagged release

.github/workflows/qc_checks.yaml

@@ -91,9 +91,6 @@ jobs:
         cache: 'pip'
     - name: Run pre-commit Checks
       uses: pre-commit/action@v2.0.3
-    - name: Check version number
-      run: |
-        python3 ci/check_version_number.py
 
   python:
     name: Tests - inventree-python