Bug 1355888 - Remove marionette.enabled pref from wptrunner; r=jgraham

MozReview-Commit-ID: IzASL0SBCsR

--HG--
extra : rebase_source : 2614e902138a6e370c024be0680458e61388d344

testing/web-platform/harness/wptrunner/browsers/firefox.py

@@ -173,8 +173,7 @@ class FirefoxBrowser(Browser):
 
         self.profile = FirefoxProfile(locations=locations,
                                       preferences=preferences)
-        self.profile.set_preferences({"marionette.enabled": True,
-                                      "marionette.port": self.marionette_port,
+        self.profile.set_preferences({"marionette.port": self.marionette_port,
                                       "dom.disable_open_during_load": False,
                                       "network.dns.localDomains": ",".join(hostnames),
                                       "network.proxy.type": 0,