[PWAs] Make sure kUserInstalled source gets added when installing locally

This CL fixes a bug where while regular user installations of
web apps would add the kUserInstalled source, locally
installing an already available from sync app would not.

Bug: 373340201
Change-Id: I023dd282d34924be6ad79125962ed29a340342eb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5931184
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Auto-Submit: Marijn Kruisselbrink <mek@chromium.org>
Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Commit-Queue: Daniel Murphy <dmurph@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1368470}