meta: add mailmap entry for garygsc

Add mailmap entry for garygsc and re-run AUTHORS to remove duplicate
entry.

PR-URL: #39588
Reviewed-By: Beth Griggs <bgriggs@redhat.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

.mailmap

@@ -147,6 +147,7 @@ Fuji Goro <gfuji@cpan.org>
 Gabriel de Perthuis <g2p.code@gmail.com>
 Gareth Ellis <gareth.ellis@uk.ibm.com> <gareth@gsellis.com>
 Garwah Lam <garwahlam@gmail.com>
+garygsc <garygsc@gmail.com> <GaryGSC@users.noreply.github.com>
 Geoffrey Bugaisky <gbugaisk@gmail.com>
 Gerhard Stöbich <deb2001-github@yahoo.de>
 Gibson Fahnestock <gibfahn@gmail.com> <gib@uk.ibm.com>

AUTHORS

@@ -2890,7 +2890,6 @@ Albert Wang <git@albertyw.com>
 Kenza Houmani <khoumani@bloomberg.net>
 mkdorff <mkdorff@outlook.com>
 xefimx <xefimix@gmail.com>
-garygsc <GaryGSC@users.noreply.github.com>
 Susana Ferreira <ssncferreira@gmail.com>
 Xavier Redondo <xavier.redondo@axa.com>
 Duncan Healy <duncan.healy@gmail.com>