Remove the bookmark provider from ContentSuggestions

The bookmarks are not currently part of ContentSuggestions on iOS.
This CL removes the provider from the ContentSuggestionsService used on iOS.

BUG=694159

Review-Url: https://codereview.chromium.org/2805703002
Cr-Commit-Position: refs/heads/master@{#462470}
1 file changed