[iOS/GN] Add code signing rules to ios_app_bundle target.

testing/test.gni

Index: testing/test.gni
diff --git a/testing/test.gni b/testing/test.gni
index 3f6f175613234cc473a9092e35e2663b8ea340a6..d7aa7cf96b3e9eb62cab9f55103b194cd4511d93 100644
--- a/testing/test.gni
+++ b/testing/test.gni
@@ -306,12 +306,6 @@ template("test") {
       if (!defined(info_plist) && !defined(info_plist_target)) {
         info_plist = "//testing/gtest_ios/unittest-Info.plist"
       }
-      if (!defined(entitlements_path)) {
-        entitlements_path = "//testing/gtest_ios"
-      }
-      if (!defined(code_signing_identity)) {
-        code_signing_identity = ""
-      }
 
       # TODO(crbug.com/603102): remove this once gyp support is dropped and all
       # application uses the target name as value for BUNDLE_ID_TEST_NAME.