mailmap: Update Mritunjay's name

Author: MritunjayTiwari14

.mailmap

@@ -20,7 +20,7 @@ Greg Price <greg@zulip.com> <gnprice@gmail.com>
 K Akhil <kssakhilraj@gmail.com>
 Lakshya Goel <lakshya1234goel@gmail.com>
 Lalit Kumar Singh <lalitkumarsingh3716@gmail.com>
-MritunjayTiwari14 <shreyashtiwari14.11@gmail.com> <shreyashtiwari14.11@gmailcom>
+Mritunjay Tiwari <shreyashtiwari14.11@gmail.com> <shreyashtiwari14.11@gmailcom>
 Rajesh Malviya <rmalviya@zulip.com> <rajveer0malviya@gmail.com>
 Shu Chen <shu@zulip.com> <shu.chen@freelancedreams.com>
 Tomlin7 <billydevbusiness@gmail.com>