improve preference label for fly/jump

indra/newview/skins/default/xui/en/panel_preferences_move.xml

@@ -133,7 +133,7 @@
    control_name="AutomaticFly"
    follows="left|top"
    height="20"
-   label="Fly/land on holding up/down"
+   label="Hold jump or crouch key to start or stop flying"
    layout="topleft"
    left_delta="0"
    name="automatic_fly"
@@ -270,4 +270,4 @@
      function="Floater.Show"
      parameter="pref_joystick" />
   </button>
-</panel>
+</panel>
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