[iOS] Prevent swipe on Discover section

Add Discover section to sections that should not allow swiping to
dismiss in the NTP.

Bug: 1085419, 1109684
Change-Id: I878c5e7a5339a130ffded7bdbd39e37f8d64b451
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2324870Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Commit-Queue: Adam Trudeau-Arcaro <adamta@google.com>
Cr-Commit-Position: refs/heads/master@{#794115}

ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller.mm

@@ -620,6 +620,7 @@ NSString* const kContentSuggestionsMostVisitedAccessibilityIdentifierPrefix =
       [self.collectionViewModel itemAtIndexPath:indexPath];
   return ![self.collectionUpdater isMostVisitedSection:indexPath.section] &&
          ![self.collectionUpdater isPromoSection:indexPath.section] &&
+         ![self.collectionUpdater isDiscoverSection:indexPath.section] &&
          [self.collectionUpdater contentSuggestionTypeForItem:item] !=
              ContentSuggestionTypeLearnMore &&
          [self.collectionUpdater contentSuggestionTypeForItem:item] !=