Remove Safari testing in SauceLabs

This is not currently possible due to missing W3C spec feautre in
[min-webdriver][0]. This has been reported in [`sinon#2372`][1].

For now, let's remove Safari from the list, so we at least can test in
the other runtimes.

[0]: mantoni/min-webdriver#31
[1]: sinonjs/sinon#2372

.min-wd

@@ -4,14 +4,7 @@
     "name": "chrome"
   }, {
     "name": "firefox"
-  }, {
-    "name": "internet explorer",
-    "version": "11"
   }, {
     "name": "MicrosoftEdge"
-  }, {
-    "name": "safari",
-    "platform": "OS X 10.11",
-    "version": "9.0"
   }]
 }