Add a Nougat Tester to chromium.android.fyi

scripts/slave/gatekeeper.json

 {
   "comment": ["This is a configuration file for gatekeeper_ng.py",
               "Look at that for documentation on this file's format."],
 
   "masters": {
     "https://build.chromium.org/p/chromium": [
       {
         "categories": [
           "chromium_tree_closer"
         ],
@@ skipping 10 matching lines @@
     ],
     "https://build.chromium.org/p/chromium.android": [
       {
         "categories": [
           "chromium_android"
         ],
         "excluded_builders": [
           "Android Swarm Builder",
           "Lollipop Consumer Tester",
           "Jelly Bean Tester",
-          "Marshmallow 64 bit Tester"
+          "Marshmallow 64 bit Tester",
+          "Nougat Phone Tester"
         ],
         "builders": {
           "Android Cronet ARM64 Builder": {
             "tree_notify": [
               "cronet-team+build@google.com"
             ],
             "closing_optional": [
               "*"
             ]
           },
@@ skipping 999 matching lines @@
         "cleanup_temp",
         "taskkill"
       ],
       "closing_optional": [
         "compile",
         "gn"
       ]
     }
   }
 }