Bug 1365638 - Change label text for "Close sidebar" to "Close Sidebar" on header menu;r=Gijs

MozReview-Commit-ID: E3rg2TUBVyn

--HG--
extra : rebase_source : 3f86cba1fee7e900577ad2d1e48b4246c481675f

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

@@ -666,7 +666,7 @@ you can use these alternative items. Otherwise, their values should be empty.  -
 <!ENTITY fullZoom.label                 "Zoom">
 <!ENTITY fullZoom.accesskey             "Z">
 
-<!ENTITY sidebarCloseButton.tooltip     "Close sidebar">
+<!ENTITY sidebarCloseButton.tooltip     "Close Sidebar">
 
 <!ENTITY quitApplicationCmdWin2.label       "Exit">
 <!ENTITY quitApplicationCmdWin2.accesskey   "x">