UI: Hide "Update Channel" label on macOS

UI/forms/OBSBasicSettings.ui

@@ -288,7 +288,7 @@
                     <enum>QFormLayout::AllNonFixedFieldsGrow</enum>
                    </property>
                    <item row="0" column="0">
-                    <widget class="QLabel" name="label_10">
+                    <widget class="QLabel" name="updateChannelLabel">
                      <property name="text">
                       <string>Basic.Settings.General.UpdateChannel</string>
                      </property>

UI/window-basic-settings.cpp

@@ -588,6 +588,8 @@ OBSBasicSettings::OBSBasicSettings(QWidget *parent)
 #elif defined(__APPLE__)
 	delete ui->updateChannelBox;
 	ui->updateChannelBox = nullptr;
+	delete ui->updateChannelLabel;
+	ui->updateChannelLabel = nullptr;
 #else
 	// Hide update section if disabled
 	if (App()->IsUpdaterDisabled())