main/mobile-config-firefox: upgrade to 1.0.1

Changes:

• https://gitlab.com/postmarketOS/mobile-config-firefox/-/tags/1.0.1

Most importantly, this provides a much better way to install the custom userChrome.css into the firefox user profile:

• mobile-config-firefox!2 (merged)

I've tested this well before merging above MR.

This upgrade MR is trivial, merging as soon as CI passes.