shared/verbs: drop unused variable

Also add a note that the function does not support multiple groups. I
think that's fair, it doesn't make sense to generalize the functionality
when we're unlikely to ever use that. (Verb options are only used by
udevadm right now.)

src/shared/options.c

@@ -525,7 +525,6 @@ int options_get_help_table_group(
         int r;
 
         assert(ret);
-        assert(ret_group);
 
         _cleanup_(table_unrefp) Table *table = NULL;
 
@@ -594,7 +593,8 @@ int options_get_help_table_group(
         }
 
         *ret = TAKE_PTR(table);
-        *ret_group = group;
+        if (ret_group)
+                *ret_group = group;
 
         assert(opt - options < INT_MAX);
         return opt - options;

src/shared/verbs.c

@@ -641,11 +641,16 @@ int _command_print_verb_help(
                                                "Option namespace %s not found.", verb->option_namespace);
 
                 _cleanup_(table_unrefp) Table *table = NULL;
-                const char *group;
-                r = options_get_help_table_group(optns, options_end, /* option_groups= */ NULL, &table, &group);
+                r = options_get_help_table_group(
+                                optns, options_end,
+                                /* option_groups= */ NULL,
+                                &table,
+                                /* ret_group= */ NULL);
                 if (r < 0)
                         return r;
 
+                /* Note: we assume that only one option group is used for a verb. If this ever
+                 * stops being true, the code here would need to be adjusted to loop over groups. */
                 help_section("Options");
                 r = table_print_or_warn(table);
                 if (r < 0)