small tweak to the XP gain text.

diff --git a/modules/PSBT_Experience.lua b/modules/PSBT_Experience.lua
index a6fe813..f8c886c 100644
--- a/modules/PSBT_Experience.lua
+++ b/modules/PSBT_Experience.lua
@@ -36,7 +36,7 @@ function PSBT_Experience:OnXPUpdated( tag, exp, maxExp, reason  )
     if ( gain <= 0 ) then
         return
     end
-    self:NewEvent( PSBT_AREAS.NOTIFICATION, true, [[/psbt/textures/exp.dds]], '+' .. tostring( gain ) .. ' XP' )
+    self:NewEvent( PSBT_AREAS.NOTIFICATION, true, [[/psbt/textures/exp.dds]], tostring( gain ) )
 end