Fix warning for Credo.Check for Elixir 1.18

Fixes a warning that some generated clauses weren't called in a static
test case

Author: rrrene

lib/credo/check.ex

@@ -457,11 +457,7 @@ defmodule Credo.Check do
 
       defoverridable Credo.Check
 
-      defp append_issues_and_timings([] = _issues, exec) do
-        exec
-      end
-
-      defp append_issues_and_timings([_ | _] = issues, exec) do
+      defp append_issues_and_timings(issues, exec) do
         Credo.Execution.ExecutionIssues.append(exec, issues)
       end
     end

lib/credo/execution/execution_issues.ex

@@ -14,6 +14,8 @@ defmodule Credo.Execution.ExecutionIssues do
   end
 
   @doc "Appends an `issue` for the specified `filename`."
+  def append(_, [] = _issues), do: :ok
+
   def append(%Execution{issues_pid: pid}, issues) when is_list(issues) do
     issues
     |> Enum.group_by(& &1.filename)