Add SEE_SUGGESTED_SITES action to Feed

Manual merge from https://chromium.googlesource.com/feed/+/8415ae95f9d6c4b1e8f118937743c6eec95bdf20

Bug: 1031666
Change-Id: I8ae830a2b9283b11c17e77b97794ac4a6adf90b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1956069Reviewed-by: Dan H <harringtond@chromium.org>
Commit-Queue: Ian Wells <iwells@chromium.org>
Cr-Commit-Position: refs/heads/master@{#723488}

components/feed/core/proto/ui/action/ui_feed_action.proto

@@ -57,6 +57,7 @@ message FeedActionMetadata {
     HIDE_ELEMENT = 13;
     SHOW_TOOLTIP = 14;
     NOT_INTERESTED_IN = 15;
+    SEE_SUGGESTED_SITES = 16;
     reserved 9, 10;  // Deprecated
   }
   optional Type type = 1;