Update chatroom reference to the new official Matrix room

We have moved from IRC to Matrix, and even the IRC references were
already wrong since we have not been on Freenode in a couple of years.

Signed-off-by: Neal Gompa <neal@gompa.dev>

README.rst

@@ -20,7 +20,7 @@ See it at work: https://pagure.io
 Playground version: https://stg.pagure.io
 
 If you have any questions or just would like to discuss about pagure,
-feel free to drop by on IRC in the channel ``#pagure`` of the freenode server
+feel free to drop by `our Matrix room <https://matrix.to/#/#pagure:fedora.im>`_.
 
 
 About its name

doc/contributing.rst

@@ -29,5 +29,5 @@ If you're submitting patches to pagure, please observe the following:
    idea but don't know how to implement it, you just have something bugging
    you?
 
-   Come to see us on IRC: ``#pagure`` or ``#fedora-apps`` on
-   irc.freenode.net or directly on `the project <http://pagure.io>`_.
+   Come to see us on Matrix: ``#pagure:fedora.im`` or directly on
+   `the project <http://pagure.io>`_.