refactor: use more consistent return types

Co-authored-by: Andrew Mayorov <encube.ul@gmail.com>

apps/emqx/src/emqx_topic_index.erl

@@ -66,7 +66,7 @@ match(Topic, Tab) ->
 
 %% @doc Match given topic against the index and return _all_ matches.
 %% If `unique` option is given, return only unique matches by record ID.
--spec matches(emqx_types:topic(), ets:table(), emqx_trie_search:opts()) -> [key(_ID)].
+-spec matches(emqx_types:topic(), ets:table(), emqx_trie_search:opts()) -> [match(_ID)].
 matches(Topic, Tab, Opts) ->
     emqx_trie_search:matches(Topic, make_nextf(Tab), Opts).