Switch to regex for banphrase regexes

[RAnders00]

Pull request checklist:

• CHANGELOG.md was updated, if applicable
• Documentation in docs/ or install-docs/ was updated, if applicable
• I have tested all changes

Fixes #1468

[zneix]

Did a little bit of testing on my own:

1. Some basic banphrases without regex weren't affected and seem to work fine.
2. Baisc regex banphrases with what re has been supporting so far works as well. I tested this with banphrases on my own pajbot instance
3. Banphrase regex mentioned in Consider migrating from "re" to "regex" library for matching regular expressions #1468 does work with this change.
4. I'm unsure whether some other advanced regexes, in e.g. #forsen would break. Maybe @Leppunen or pajlada can help with this one. Though, as far as I can tell based on my lidl research, nothing should break. See point 3. https://github.com/alvations/sacremoses/issues/76#issuecomment-590047152

[pajlada]

Tested on a bunch of production banphrases, and things seem to work as expected. LGTM 👍