Update locked frozendict version to 2.3.2 (#13284)

`frozendict` 2.3.2 includes a fix for a memory leak in
`frozendict.__hash__`. This likely has no impact outside of the
deprecated `/initialSync` endpoint, which uses `StreamToken`s,
containing `RoomStreamToken`s, containing `frozendict`s, as cache keys.

Signed-off-by: Sean Quah <seanq@matrix.org>