The matrix integration folder in python-zulip-api changed its name from matrix to bridge_with_matrix but this was not reflected in the docs. Change the docs accordingly. Solves issue #545 in the python-zulip-api directory.
This is a follow-up to #9491.
'install-matrix' is used twice, in 'integrations/irc.md' and 'integrations/matrix.md'. Hence we create a macro for it.