Remove compiler field from iOS bot configs, ensure gn_args match configuration

ios/build/bots/chromium.mac/ios-device-xcode-clang.json

Index: ios/build/bots/chromium.mac/ios-device-xcode-clang.json
diff --git a/ios/build/bots/chromium.mac/ios-device-xcode-clang.json b/ios/build/bots/chromium.mac/ios-device-xcode-clang.json
index 9d3e7e248b8b271cc123db14e0c01ee9c3c2797a..0102de56f433fa2c4d9d5f993b951f274533e683 100644
--- a/ios/build/bots/chromium.mac/ios-device-xcode-clang.json
+++ b/ios/build/bots/chromium.mac/ios-device-xcode-clang.json
@@ -1,8 +1,4 @@
 {
-  "owners": [
-    "sdefresne",
-    "smut"
-  ],
   "comments": [
     "Builder for 32-bit devices.",
     "Build is performed with gn+ninja."
@@ -13,7 +9,7 @@
     "goma_dir=\"$(goma_dir)\"",
     "ios_enable_code_signing=false",
     "is_component_build=false",
-    "is_debug=true",
+    "is_debug=false",
     "target_cpu=\"arm\"",
     "target_os=\"ios\"",
     "use_goma=true",
@@ -22,7 +18,6 @@
   "additional_compile_targets": [
     "all"
   ],
-  "compiler": "ninja",
   "configuration": "Release",
   "sdk": "iphoneos10.0",
   "tests": [