Bug 1604011 - Remove dead assignment from StreamLoader::OnStopRequest. r=emilio,xidorn

Differential Revision: https://phabricator.services.mozilla.com/D57235

--HG--
extra : moz-landing-system : lando

layout/style/StreamLoader.cpp

@@ -69,7 +69,6 @@ StreamLoader::OnStopRequest(nsIRequest* aRequest, nsresult aStatus) {
     if (rv != NS_OK_PARSE_SHEET) {
       return rv;
     }
-    rv = NS_OK;
 
     // BOM detection generally happens during the write callback, but that won't
     // have happened if fewer than three bytes were received.