[dPWA] Clean up some unnecessary includes affecting many targets.

This removes some heavy includes for a file that is included by the
web_app_constants.h file. There is a bug filed for further improvement
to redo the Manifest::* classes to just be regular classes.

Change-Id: I33025979cd78f4c05801318fb66b538b000e4f4c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4349869


Commit-Queue: Daniel Murphy <dmurph@chromium.org>
Reviewed-by: Dibyajyoti Pal <dibyapal@chromium.org>
Commit-Queue: Dibyajyoti Pal <dibyapal@chromium.org>
Auto-Submit: Daniel Murphy <dmurph@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1118943}