.mailmap: update Fangrui's email

I'm leaving Google.

Link: https://lkml.kernel.org/r/20240927192912.31532-1-i@maskray.me
Signed-off-by: Fangrui Song <i@maskray.me>
Acked-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: MaskRay

.mailmap

@@ -203,6 +203,7 @@ Ezequiel Garcia <ezequiel@vanguardiasur.com.ar> <ezequiel@collabora.com>
 Faith Ekstrand <faith.ekstrand@collabora.com> <jason@jlekstrand.net>
 Faith Ekstrand <faith.ekstrand@collabora.com> <jason.ekstrand@intel.com>
 Faith Ekstrand <faith.ekstrand@collabora.com> <jason.ekstrand@collabora.com>
+Fangrui Song <i@maskray.me> <maskray@google.com>
 Felipe W Damasio <felipewd@terra.com.br>
 Felix Kuhling <fxkuehl@gmx.de>
 Felix Moeller <felix@derklecks.de>