Bug 1147716 - Remove offline mode observer in browser_bug435325.js. r=jimm

browser/base/content/test/general/browser_bug435325.js

@@ -59,6 +59,7 @@ function checkPage() {
   Services.obs.addObserver(function observer(aSubject, aTopic) {
     ok(!Services.io.offline, "After clicking the Try Again button, we're back " +
                              "online.");
+    Services.obs.removeObserver(observer, "network:offline-status-changed", false);
     finish();
   }, "network:offline-status-changed", false);
   gBrowser.contentDocument.getElementById("errorTryAgain").click();