Remove it from request handler since there's already the context of the
request path, added through TraceLayer.

They are no longer needed in the 2021 edition.

Upgrades Ruma again to make this work.

Co-authored-by: Timo Kösters <timo@koesters.xyz>

json_body is used in places that need authentication. In
case an unknown field is set, Ruma doesn't parse the field
and so doesn't give an error on invalid UTF-8. But Conduit
has parsed and on error makes json_body None. Return an
error to the client instead of generating an internal error.

… and refactor push rule code along the way.