[iOS][MF] Don't allow row selection

Not explicitly disabling row selection would cause Voice Over to read
"selected" on double taps.

Bug: 845472
Change-Id: If41b29356a86b6ae2bad9ffd365c68a46c7c5cb1
Reviewed-on: https://chromium-review.googlesource.com/c/1352158Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611151}

ios/chrome/browser/ui/autofill/manual_fill/fallback_view_controller.mm

@@ -63,6 +63,7 @@ constexpr float PopoverMaxHeight = 250;
   self.tableView.sectionFooterHeight = 20.0;
   self.tableView.estimatedRowHeight = 200;
   self.tableView.separatorInset = UIEdgeInsetsMake(0, 0, 0, 0);
+  self.tableView.allowsSelection = NO;
   self.definesPresentationContext = YES;
 }