Investigate whether this workaround is still needed re: dropping resource header

https://github.com/googleapis/nodejs-firestore/blob/7a9d17bdd5fca3d91e66f7500c035140a7397c33/owlbot.py#L33

The code above references a workaround that we implemented because the GAPIC library was dropping the resource header (circa 2018). I think that this issue has been addressed in later versions, and if we can remove this it will simplify the post-processing we have to do.