Remove deprecated state column from issues and merge_requests

state column has been marked as ignored on !19574 (merged) and now can be safely removed.

Following our updated guidelines this will need two merge requests:

1. Remove the column from database - Done: !25561 (merged)
2. Remove the ignore rule - Done: !27690 (merged)

The following discussion from !19574 (merged) should be addressed:

• @smcgivern started a discussion:

  Can you please create an issue in 12.7 to remove these lines, and then link to it in a code comment? (It's not documented yet, but will be soon. cc @abrandl)