Bug 1537726 - Further clean up the regex for legacy homepage reset. r=r1cky

Differential Revision: https://phabricator.services.mozilla.com/D24333

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

browser/components/BrowserGlue.jsm

@@ -2593,7 +2593,7 @@ BrowserGlue.prototype = {
         const DEFAULT = Services.prefs.getDefaultBranch(HOMEPAGE_PREF).getCharPref("");
         let value = Services.prefs.getCharPref(HOMEPAGE_PREF);
         let updated = value.replace(
-          /https?:\/\/([\w\-]+[.])?start[\d]*\.mozilla\.(org|com)[^|]*/ig, DEFAULT);
+          /https?:\/\/([\w\-]+\.)?start\d*\.mozilla\.(org|com)[^|]*/ig, DEFAULT);
         if (updated != value) {
           if (updated == DEFAULT) {
             Services.prefs.clearUserPref(HOMEPAGE_PREF);