Remove ContentSuggestionsProvider::GetProvidedCategories().
Since there is ContentSuggestionsProvider::Observer::OnCategoryStatusChanged(),
there is no need for ContentSuggestionsProvider::GetProvidedCategories().
BUG=
639282
Committed:
https://crrev.com/47a8bf5b772e8b3f50e67791c1c2990a12004158
Cr-Commit-Position: refs/heads/master@{#413428}