Remove ignore rules for pre_receive_secret_detection_enabled

What does this MR do and why?

This deletes the ignore rules as per the guide for:

• application_settings.pre_receive_secret_detection_enabled
• project_security_settings.pre_receive_secret_detection_enabled

After the columns were cleaned up in #515382 (closed).

This can only be merged in the next milestone after !189724 (merged) is merged.

References

• #515382 (closed)
• #512996 (closed)

MR acceptance checklist

I have evaluated this MR against the MR acceptance checklist.