Mark 2 calculations in raw_ptr_asan_unowned.cc as PA_UNSAFE_TODO

Bug: 510915930
Change-Id: I2d3dfd25240825e04b8a2b65ddca2c04e9c0db3c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7831823
Reviewed-by: Stephen Nusko <nuskos@chromium.org>
Commit-Queue: Stephen Nusko <nuskos@chromium.org>
Auto-Submit: Fergal Daly <fergal@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1627499}
NOKEYCHECK=True
GitOrigin-RevId: 8779a41a5f26682a87af8aa6b18e85b20e3355f7