Disable WKHTTPSystemCookieStore usage

Bug: 833872
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I6c06c7e031dd2fcf8569c377e1d4696b45e007ca
Reviewed-on: https://chromium-review.googlesource.com/1014714Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Mohammad Refaat <mrefaat@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551369}

ios/web/features.mm

@@ -17,7 +17,7 @@ const base::Feature kNewFileDownload{"NewFileDownload",
                                      base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kWKHTTPSystemCookieStore{"WKHTTPSystemCookieStore",
-                                             base::FEATURE_ENABLED_BY_DEFAULT};
+                                             base::FEATURE_DISABLED_BY_DEFAULT};
 
 }  // namespace features
 }  // namespace web