fix-missing-self-or-cls is missing self.node_is_selected check

[clavedeluna]

All codemods should have logic similar to self.node_is_selected to check if results exist for this codemod. When writing this codemod we forgot to update sonar_issues.json which made the integration test for this codemod pass. However, adding the self.node_is_selected would've alerted us to having forgotten to add a corresponding sonar issue.

[drdavella]

I'm curious whether this failure is related: https://github.com/pixee/codemodder-python/actions/runs/8420800708/job/23056254528