Remove ignored AI application settings columns

Problem to Solve

Post removal of the following columns, we can also remove these columns ignored columns in the application record in the %17.10 milestone.

After all the columns ignored columns are removed, we should have no more references to old AI setting keys. https://gitlab.com/gitlab-org/gitlab/-/blob/c255c467fa4d2e4831d4e46196bdba799b426b26/app/models/application_setting.rb#L10-19

Implementation

Remove the following columns in the %17.10 milestone.

  ignore_columns %i[
    encrypted_openai_api_key
    encrypted_openai_api_key_iv
    encrypted_anthropic_api_key
    encrypted_anthropic_api_key_iv
    encrypted_vertex_ai_credentials
    encrypted_vertex_ai_credentials_iv
    encrypted_vertex_ai_access_token
    encrypted_vertex_ai_access_token_iv
  ], remove_with: '17.5', ...

Definition of Done

No more references exist of the following columns in the application_settings table.