Controller Applet had instance of Undocked, make Handheld

Remember that time we renamed the Undocked option to Handheld in the
status bar, and then later remembered the Controller Configuration?

Scrolling through Transifex I noticed that we still have one instance of
"Undocked" in the text.

src/yuzu/applets/qt_controller.ui

@@ -2300,7 +2300,7 @@
             <item>
              <widget class="QRadioButton" name="radioUndocked">
               <property name="text">
-               <string>Undocked</string>
+               <string>Handheld</string>
               </property>
              </widget>
             </item>