Drop no_clause_has_guards condition when checking exhaustiveness

Since too complex guards lead to skipping a function altogether now,
this condition is redundant.
Dropping it allows exhaustiveness checking to benefit from the simple
refinements from guards that are supported.

src/typechecker.erl

@@ -3998,7 +3998,6 @@ disable_exhaustiveness_check(#env{} = Env) ->
 check_arg_exhaustiveness(Env, ArgTys, Clauses, RefinedArgTys) ->
     case exhaustiveness_checking(Env) andalso
          all_refinable(ArgTys, Env) andalso
-         no_clause_has_guards(Clauses) andalso
          some_type_not_none(RefinedArgTys)
     of
         true ->
@@ -4019,10 +4018,6 @@ exhaustiveness_checking(#env{} = Env) ->
 all_refinable(any, _Env) -> false;
 all_refinable(Types, Env) -> lists:all(fun (Ty) -> refinable(Ty, Env) end, Types).
 
--spec no_clause_has_guards(_) -> boolean().
-no_clause_has_guards(Clauses) ->
-    lists:all(fun no_guards/1, Clauses).
-
 -spec some_type_not_none([type()]) -> boolean().
 some_type_not_none(Types) when is_list(Types) ->
     lists:any(fun (T) -> T =/= type(none) end, Types).
@@ -4564,10 +4559,6 @@ mta({user_type, Anno, Name, Args}, Env) ->
 mta(Type, _Env) ->
     Type.
 
--spec no_guards(_) -> boolean().
-no_guards({clause, _, _, Guards, _}) ->
-    Guards == [].
-
 %% Refines the types of bound variables using the assumption that a clause has
 %% mismatched.
 -spec refine_vars_by_mismatching_clause(gradualizer_type:af_clause(), venv(), env()) -> venv().