Keep documented return values after changing Mix.State to use :ets (#12017)

Author: michallepicki

lib/mix/lib/mix/state.ex

@@ -36,10 +36,12 @@ defmodule Mix.State do
 
   def put(key, value) do
     :ets.insert(@name, {key, value})
+    :ok
   end
 
   def update(key, fun) do
     :ets.insert(@name, {key, fun.(:ets.lookup_element(@name, key, 2))})
+    :ok
   end
 
   ## Persistent term cache (persistent, cleared in tests)

lib/mix/lib/mix/tasks_server.ex

@@ -17,6 +17,7 @@ defmodule Mix.TasksServer do
 
   def put(tuple) do
     :ets.insert(@name, {tuple})
+    :ok
   end
 
   def get(tuple) do
@@ -29,5 +30,6 @@ defmodule Mix.TasksServer do
 
   def clear() do
     :ets.delete_all_objects(@name)
+    :ok
   end
 end