Add IQY and ZST to download_file_types.asciipb

These could provide some extra friction for users with Safe Browsing
disabled who download these possibly-dangerous file types.

Fixed: 40068800, 40063014
Change-Id: I8e0b206e01cb50f4ff852dacf4aedf1db050a713
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5605695


Commit-Queue: Daniel Rubery <drubery@chromium.org>
Reviewed-by: Lily Chen <chlily@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1313134}