doc: posix: mark pthread_rwlockattr_setpshared as supported

Mark pthread_rwlockattr_setpshared() and
pthread_rwlockattr_getpshared() as supported in the POSIX
Options documentation.

Signed-off-by: Christopher Friedt <cfriedt@meta.com>

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

@@ -401,9 +401,9 @@ _POSIX_READER_WRITER_LOCKS
     pthread_rwlock_unlock(),yes
     pthread_rwlock_wrlock(),yes
     pthread_rwlockattr_destroy(),yes
-    pthread_rwlockattr_getpshared(),
+    pthread_rwlockattr_getpshared(),yes
     pthread_rwlockattr_init(),yes
-    pthread_rwlockattr_setpshared(),
+    pthread_rwlockattr_setpshared(),yes
 
 .. _posix_option_thread_attr_stackaddr: