Rename chromium.mac iOS bots

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 343 matching lines @@
       {
         "categories": [
           "chromium_tree_closer"
         ],
         "comment": [
           "TODO(dpranke): crbug.com/486089, crbug.com/439402",
           "Until the Mac GN (dbg) bot is in the CQ, it should not close the",
           "tree."
         ],
         "builders": {
-          "iOS_Device": {
+          "ios-device": {
             "sheriff_classes": ["sheriff_ios_europe", "sheriff_ios_us"]
           },
-          "iOS_Simulator_(dbg)": {
+          "ios-simulator": {
             "sheriff_classes": ["sheriff_ios_europe", "sheriff_ios_us"],
             "closing_optional": [],
             "comment": ["closing_optional due to crbug.com/393861"]
           },
-          "iOS_Device_(ninja)": {
-            "sheriff_classes": ["sheriff_ios_europe", "sheriff_ios_us"]
-          },
           "Mac GN (dbg)": {
             "close_tree": false
           },
           "*": {}
         }
       }
     ],
     "https://build.chromium.org/p/chromium.memory": [
       {
         "categories": [
@@ skipping 570 matching lines @@
         "cleanup_temp",
         "taskkill"
       ],
       "closing_optional": [
         "compile",
         "gn"
       ]
     }
   }
 }