Updated `DCHECK` to `if` check.

Update is consistent to the `GridViewController` (https://source.chromium.org/chromium/chromium/src/+/main:ios/chrome/browser/ui/tab_switcher/tab_grid/grid/grid_view_controller.mm;l=775?q=didEndDisplayingCell&ss=chromium%2Fchromium%2Fsrc).

Fixed: 1418011
Change-Id: I81e49c97862a8b093537201d7835a9ae1a05e4cc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4286716


Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Petro Akzhygitov <pakzhygitov@google.com>
Cr-Commit-Position: refs/heads/main@{#1108987}