UI: Make "output mode" label disabled if active

I had previous made the output mode list box become disabled, but
neglected to do it for the label as well.

obs/forms/OBSBasicSettings.ui

@@ -271,7 +271,7 @@
              <enum>QFormLayout::AllNonFixedFieldsGrow</enum>
             </property>
             <item row="0" column="0">
-             <widget class="QLabel" name="label_16">
+             <widget class="QLabel" name="outputModeLabel">
               <property name="minimumSize">
                <size>
                 <width>170</width>

obs/window-basic-settings.cpp

@@ -831,6 +831,7 @@ void OBSBasicSettings::LoadOutputSettings()
 
 	if (video_output_active(obs_get_video())) {
 		ui->outputMode->setEnabled(false);
+		ui->outputModeLabel->setEnabled(false);
 		ui->advOutTopContainer->setEnabled(false);
 		ui->advOutRecTopContainer->setEnabled(false);
 		ui->advOutRecTypeContainer->setEnabled(false);