Revert^3 "Visit URIs in intents associated with notifications."

This reverts commit c82df289.

Reason for revert: this was fixing a hypothetical vulnerability, but we decided that it's safer to not actually check intents at this point; for more information, see b/281044385#comment62

Note: I also removed the TODOs about checking intents, rather than
adding them back.

Change-Id: I19a700bdf12a131a6421341343d4dec55bfe2319