Update ignore list for directives tracking (#303)

Remove warnings for nranks and omp_num_threads being specified but unused because they are automatically specified by groups now (whether or not the user specifies them).

flow/project.py

@@ -2714,7 +2714,7 @@ def _msg(group):
             keys_unused = {
                 key for op in operations for key in
                 op.directives._keys_set_by_user.difference(op.directives.keys_used)
-                if key not in ('fork', )  # whitelist
+                if key not in ('fork', 'nranks', 'omp_num_threads')  # ignore list
             }
             if keys_unused:
                 logger.warning(