Update iOS GN templates.

The test template was forwarding output_name and output_extension to the ios_app template, but that isn't used by the ios_app template. If somebody actually uses this value, they'll get an error, so it's better to not pretend to support it.

The test template also forwarded visibility which was never used by ios_app. This should be used so is now hooked up to the group generated by ios_app.

Review URL: https://codereview.chromium.org/1801833002

Cr-Original-Commit-Position: refs/heads/master@{#381057}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 71f8ea104d391816e5ca040534dcc3b288b0a59b

config/ios/rules.gni

@@ -180,6 +180,7 @@ template("ios_app") {
 
   # Top level group
   group(target_name) {
+    forward_variables_from(invoker, [ "visibility" ])
     deps = [
       ":$bin_gen_target_name",
       ":$plist_gen_target_name",