doc: posix: mark set and get inheritsched as supported

`pthread_attr_getinheritsched()` and
`pthread_attr_setinheritsched()` are now implemented,
mark it so.

signed-off-by: Gaetan Perrot <gaetanperrotpro@gmail.com>

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

@@ -438,10 +438,10 @@ _POSIX_THREAD_PRIORITY_SCHEDULING
    :header: API, Supported
    :widths: 50,10
 
-    pthread_attr_getinheritsched(),
+    pthread_attr_getinheritsched(),yes
     pthread_attr_getschedpolicy(),yes
     pthread_attr_getscope(),
-    pthread_attr_setinheritsched(),
+    pthread_attr_setinheritsched(),yes
     pthread_attr_setschedpolicy(),yes
     pthread_attr_setscope(),
     pthread_getschedparam(),yes