doc: posix: Update POSIX supported API documentation

Updates in documentation support for `mq_notify` API
in `_POSIX_MESSAGE_PASSING` group option.

Signed-off-by: Adam Wojasinski <[email protected]>

Author: awojasinski

doc/services/portability/posix/option_groups/index.rst

@@ -359,7 +359,7 @@ _POSIX_MESSAGE_PASSING
 
     mq_close(),yes
     mq_getattr(),yes
-    mq_notify(),
+    mq_notify(),yes
     mq_open(),yes
     mq_receive(),yes
     mq_send(),yes