Merge commit '2e5bde95'

* commit '2e5bde95':
  h264: eliminate max_contexts

This commit is a noop as max_contexts can change and mismatch the
nb_slice_ctx (see 507b01f8).

The file in the Ticket is not decodable anymore, so it was not possible
to check if that code path was triggerable some way or another, or even
test a different fix.
Merged-by: Clément Bœsch <clement@stupeflix.com>