ios: ignore deprecated GTM function

This function is deprecated as of GTM 85341176, which we are about to roll past.

Bug: 386671
Change-Id: I134cca2c9c2252ceaa63facb289ac907a1774696
Reviewed-on: https://chromium-review.googlesource.com/c/1478498
Auto-Submit: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#633738}

ios/chrome/test/google_toolbox_unittest.mm

@@ -15,9 +15,14 @@
 
 using GoogleToolboxForMacTest = PlatformTest;
 
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+
 // [NSDictionary gtm_dictionaryWithHttpArgumentsString] is used downstream.
 // This test ensures that we keep compiling the file.
 TEST_F(GoogleToolboxForMacTest, dictionaryWithHttpArgumentsString) {
   NSDictionary* dict = [NSDictionary gtm_dictionaryWithHttpArgumentsString:@""];
   EXPECT_EQ(0u, [dict count]);
 }
+
+#pragma clang diagnostic pop