Yannis Roussos authored Apr 07, 2020 and Mayra Cabrera committed Apr 20, 2020

- Add Migration/String cop to enforce usage of the text
  data type instead of string
- Remove the existing Migration/AddLimitToStringColumns
  cop and its rspec tests as strings are no longer allowed
- Add Migration/Text cop to enforce limit on text columns
- Add rspec tests for the Migration/String and
  the Migration/Text cops
- Disable the offenses caused by existing migrations with
  strings or texts without limits