Remove warning introduced by an unused variabled into NS_NewFileSpecWithSpec.

xpcom/io/nsFileSpecImpl.cpp

@@ -624,7 +624,6 @@ NS_METHOD nsFileSpecImpl::Create(nsISupports* outer, const nsIID& aIID, void* *a
 nsresult NS_NewFileSpecWithSpec(nsFileSpec aSrcFileSpec, nsIFileSpec **result)
 //----------------------------------------------------------------------------------------
 {
-	nsresult rv = NS_OK;
 	if (!result)
 		return NS_ERROR_NULL_POINTER;