[dPWA] Remove the kCreateShortcutIgnoresManifest feature.

This feature is not going to ship due to a conflict with a first party
partner needing the manifest to be used, and how we are soon launching
universal install (install any site) and changing create shortcut to not
create apps.

Bug: 40184819,40247850
Change-Id: Id61867c0b7d67c6ff4038177124b12d39609e668
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5417154


Auto-Submit: Daniel Murphy <dmurph@chromium.org>
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1282164}