Closes #292

What was going on:

1. This commit increments the version as transformers v.4.22 in _versions.yml
2. But afterwards immediately, this commit removes v4.22 from _versions.yml when transformers.version changes back to dev mode

The explanation is that step2 had "old" _version.yml file before step1 finished committing the "new" _versions.yml

As a solution, we will not commit changes to _versions.yml when the branch is main

cc: @sgugger @LysandreJik