Bug 656021 - Update Scratchpad menu access key to S; r=l10n

browser/locales/en-US/chrome/browser/browser.dtd

@@ -205,7 +205,7 @@ can reach it easily. -->
   -  approximation to it or choose a word (or words) that means
   -  "simple discardable text editor". -->
 <!ENTITY scratchpad.label             "Scratchpad">
-<!ENTITY scratchpad.accesskey         "r">
+<!ENTITY scratchpad.accesskey         "s">
 <!ENTITY scratchpad.keycode           "VK_F4">
 <!ENTITY scratchpad.keytext           "F4">