Log Message:
Update chat/mautrix-python to 0.7.13

According to the author, this should now work with Python 3.9, so I'm removing
39 from PYTHON_VERSIONS_INCOMPATIBLE, as well as for all packages that had it
because they depend on mautrix-python.

v0.7.13
Extended session wait time when handling encrypted messages in bridges: it'll
now wait for 5 seconds, then send an error, then wait for 10 more seconds. If
the keys arrive in those 10 seconds, the message is bridged and the error is
redacted, otherwise the error is edited.

v0.7.12
No change log was released