Fix to re-run `CollectInlines` when turning on/off `initial-letter`

The `initial-letter` creates a special `InlineItem` with the
`kInitialLetter` type in the parent IFC. This patch fixes to
re-run `CollectInlines` for the parent IFC when it's turned
on or off.

Fixed: 342802976
Change-Id: If1ef00fb74c961bb065a4df8d5e8c9ad48860711
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5612813


Commit-Queue: Kent Tamura <tkent@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Auto-Submit: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1312632}