mailmap: Add entry for Parth.
mailmap: Add entry for Parth.

Guessing with the capitalized form, which is also the one they've
used slightly more often.

zulip/zulip,rht/zulip,andersk/zulip,rht/zulip,zulip/zulip,kou/zulip,andersk/zulip,rht/zulip,kou/zulip,kou/zulip,kou/zulip,rht/zulip,zulip/zulip,kou/zulip,andersk/zulip,zulip/zulip,zulip/zulip,zulip/zulip,andersk/zulip,kou/zulip,andersk/zulip,rht/zulip,andersk/zulip,kou/zulip,zulip/zulip,rht/zulip,rht/zulip,andersk/zulip