Fix MB config for ios-simulator-cronet.

TBR=smut@google.com
BUG=

Review-Url: https://codereview.chromium.org/2195213002
Cr-Commit-Position: refs/heads/master@{#408892}

ios/build/bots/chromium.mac/ios-simulator-cronet.json

@@ -22,7 +22,7 @@
   ],
   "gn_args": [
     "additional_target_cpus=[\"x86\"]",
-    "component=static_library",
+    "is_component_build=false",
     "disable_brotli_filter=true",
     "disable_file_support=true",
     "disable_ftp_support=true",