test: clean up reward-hacking backend tests (#5563)

controller/channel_upstream_update_test.go

@@ -81,10 +81,6 @@ func TestCollectPendingApplyUpstreamModelChanges(t *testing.T) {
 	require.Equal(t, []string{"old-model"}, pendingRemoveModels)
 }
 
-func TestChannelUpstreamModelUpdateSelectFieldsIncludeModelMapping(t *testing.T) {
-	require.Contains(t, channelUpstreamModelUpdateSelectFields, "model_mapping")
-}
-
 func TestNormalizeChannelModelMapping(t *testing.T) {
 	modelMapping := `{
 		" alias-model ": " upstream-model ",