Update check_documentation.yml (#230)

added hash to upload-artifact action

Author: berndgassmann

.github/workflows/check_documentation.yml

@@ -44,7 +44,7 @@ jobs:
         bash .github/workflows/code_coverage.sh
 
     - name: Upload coverage as artifact
-      uses: actions/upload-artifact@v4
+      uses: actions/upload-artifact@0b2256b8c012f0828dc542b3febcab082c67f72b # v4.3.4
       with:
         name: coverage_report
         path: ./coverage