GUI: More concise text for length settings

GUI/mainwindow/actionmanager.cpp

@@ -263,8 +263,8 @@ void ActionManager::onAboutToShowSettingsMenu()
         unitActions->addAction(action);
     };
 
-    addUnitAction("Use nanometer as default unit", false);
-    addUnitAction(u8"Use \u00c5ngstrom as default unit", true);
+    addUnitAction("Lengths in nanometer", false);
+    addUnitAction(u8"Lengths in \u00c5ngstrom", true);
 
     m_settingsMenu->addSeparator();