[Chore] Remove Commit from typeorm

[crutchcorn]

We originally wanted to save the last 5 commits to the on-device DB for performance reasons back when we were considering using ismorphic-git. Now, with native code powering git log, we don't feel the need to do this anymore. However, we want to include a migration to remove Commit table from the SQLite database:

https://stackoverflow.com/questions/59101285/how-to-deal-with-sqlite-migrations-in-react-native-using-typeorm

[crutchcorn]

Blocked by upstream issue:

typeorm/typeorm#7829