sepolicy: fix comments around 'domain' access to search in /vendor

Effectively removes TODOs and finalizes the initial solution to allow
all domains access to 'vendor_file'.

Bug: 36681074
Test: Build and boot sailfish (no policy changes in the CL)

Change-Id: I50c05e20175c5273b34901809d967dd3e48bdb0e
Signed-off-by: Sandeep Patil <sspatil@google.com>