Tidy up various tryCatch statements when upstream fixes get implemented

[ateucher]

We currently have workarounds for a couple of issues/bugs in usethis:

• create_from_bcgov_github() has this and use_bcgov_github() has this, both of which should be able to be removed when this hits CRAN
• use_bcgov_template() has this, which should be removed if this gets accepted.

[ateucher]

the tryCatch around use_template() is gone in #46, but the git2r ones remain... It's possible they can be removed with the latest updates to usethis and git2r, but I haven't tested yet.