chore: simplify regex

[msopacua]

• We already do toLowerCase(), so don't need i flag.
• We're not using the http bit, so no need to capture it.
• If there's an s, append it, if not don't. This is the same as just replacing http with ws:
  • [http]:// -> [ws]://
  • [http]s:// -> [ws]s://
  • [http]x:// -> [ws]x:// -> error. Is ok.
  • [http]sx:// -> [ws]sx:// -> error in both. Is ok.
• We don't want to replace protocols that do not start with http, such as git+https, so we can anchor at string start and leave out the g flag.

Much simpler -:)

[lukeocodes]

Oh it's possible this is different as of #273, I can't remember if I replaced this code or moved it