Remove column from project_settings

What does this MR do?

Remove column from project_settings

This commit removes project_settings.allow_editing_commit_messages column. The column was previously ignored in %14.2, following the process for column removal, the column can now be removed in %14.3.

Related to #336783 (closed)

14:35:08 ❯ rails db:migrate
== 20210823193234 RemoveAllowEditingCommitMessagesFromProjectSettings: migrating
-- remove_column(:project_settings, :allow_editing_commit_messages)
   -> 0.0028s
== 20210823193234 RemoveAllowEditingCommitMessagesFromProjectSettings: migrated (0.0195s)

14:36:02 ❯ rails db:migrate:down VERSION=20210823193234
== 20210823193234 RemoveAllowEditingCommitMessagesFromProjectSettings: reverting
-- add_column(:project_settings, :allow_editing_commit_messages, :boolean, {:default=>false, :null=>false})
   -> 0.0028s
== 20210823193234 RemoveAllowEditingCommitMessagesFromProjectSettings: reverted (0.0208s)

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• [-] I have added/updated documentation, or it's not needed. (Is documentation required?)
• [-] I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.