MM-25544:Update error message for length violations (#14853)

* update error message for length violations

* fix unit test

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

store/storetest/group_store.go

@@ -148,7 +148,7 @@ func testGroupStoreCreate(t *testing.T, ss store.Store) {
 	require.Nil(t, g5.IsValidForCreate())
 
 	g5.Name = model.NewString(*g5.Name + "x")
-	require.Equal(t, g5.IsValidForCreate().Id, "model.group.name.app_error")
+	require.Equal(t, g5.IsValidForCreate().Id, "model.group.name.invalid_length.app_error")
 	g5.Name = model.NewString(model.NewId())
 	require.Nil(t, g5.IsValidForCreate())