Skip linters for redmine 4.2

Author: simon-isler

.github/workflows/validation.yml

@@ -59,6 +59,7 @@ jobs:
           GITHUB_ACTIONS: true
 
       - name: Run linters
+        if: matrix.redmine-version != '4.2-stable'
         working-directory: plugins/redmine_tracky
         run: bundle exec rake lint