[PWA] Fix IncompatibleAppShim integration test.

Unfortunately this test broke while being unintentionally disabled.
Fix the test by adding a flag to allow the LaunchFromAppShim call
inside the LaunchFromPlatformShortcut call to fail, as in this
specific test the initial launch will fail, even though the eventual
app launch still succeeds.

Bug: 386749842
Change-Id: If38ff1663c28abc25d362f7593a8a60445327ccf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6133859
Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1401517}