codecs: rename MakeCodecs rename and docs update (#8245)

* codecs: rename MakeCodecs to MakeTestCodecs

* update changelog

* remove MakeTestCodecs

* typo

x/staking/simulation/decoder_test.go

@@ -32,9 +32,8 @@ func makeTestCodec() (cdc *codec.LegacyAmino) {
 }
 
 func TestDecodeStore(t *testing.T) {
-	cdc, _ := simapp.MakeCodecs()
+	cdc := simapp.MakeTestEncodingConfig().Marshaler
 	dec := simulation.NewDecodeStore(cdc)
-
 	bondTime := time.Now().UTC()
 
 	val, err := types.NewValidator(valAddr1, delPk1, types.NewDescription("test", "test", "test", "test", "test"))