UI: Clarify replay buf. hotkey error message

It should specify that the user specifically needs to set the "save"
hotkey, not just "the replay buffer hotkey".

UI/data/locale/en-US.ini

@@ -125,7 +125,7 @@ Output.RecordNoSpace.Msg="There is not sufficient disk space to continue recordi
 Output.RecordError.Title="Recording error"
 Output.RecordError.Msg="An unspecified error occurred while recording."
 Output.ReplayBuffer.NoHotkey.Title="No hotkey set!"
-Output.ReplayBuffer.NoHotkey.Msg="No hotkey set for replay buffer.  Please set a hotkey to use for saving replay recordings."
+Output.ReplayBuffer.NoHotkey.Msg="No save hotkey set for replay buffer.  Please set the \"Save\" hotkey to use for saving replay recordings."
 
 # output recording messages
 Output.BadPath.Title="Bad File Path"