Bug 1132566 - Enable test in e10s: browser_privatebrowsing_cache.js; r=billm

This test appeared to run fine under e10s, so after running 30 times
with "mochitest-browser --e10s --run-until-failure" I've re-enabled it.

--HG--
extra : rebase_source : ff82148650f54bc66cccd08abae9c10cba9f2bed

browser/components/privatebrowsing/test/browser/browser.ini

@@ -22,7 +22,6 @@ skip-if = true # Bug 1142678 - Loading a message sending frame script into a pri
 skip-if = e10s
 [browser_privatebrowsing_aboutSessionRestore.js]
 [browser_privatebrowsing_cache.js]
-skip-if = e10s
 [browser_privatebrowsing_certexceptionsui.js]
 skip-if = e10s
 [browser_privatebrowsing_concurrent.js]