[test] IE8 is no longer supported by Saucelabs

Ref: https://wiki.saucelabs.com/display/DOCS/2018/10/16/Announcing+End+of+Life+for+Internet+Explorer+8+on+Windows+7

Author: darrachequesne

zuul.config.js

@@ -36,7 +36,7 @@ zuulConfig.browsers = [
     version: 'latest'
   }, {
     name: 'internet explorer',
-    version: '8..11'
+    version: '9..11'
   }, {
     name: 'safari',
     version: 'latest'