rust-index: drop offset_override
The inline `offsets` value diverge from the one on disk for added value, so the
offset_override tricks is not going to work well once we start having the full
revlog logic in Rust.
We remove it beforehand and align the Rust logic to the Python one (adjusting
the segment offset at read time for inline revlog).
# So GitLab doesn't think we're using tons of Perl
*.t -linguist-detectable