Summary:
Rename TestPgRegressGenerated to TestPgRegressPgGenerated to keep it consistent with other child classes of BasePgRegressTestPorted.
Jira: DB-13679

Test Plan: Jenkins: test regex: TestPgRegressPgGenerated*

Reviewers: stiwary

Reviewed By: stiwary

Subscribers: yql

Differential Revision: https://phorge.dev.yugabyte.com/D39461