Bump version to v0.2.9 (astral-sh#4107)

Bump version to 0.2.8 (astral-sh#4076)

Update pubgrub to new `add_incompatibility_from_dependencies` (astral…

…-sh#4062)

We had previously changed the signature of
`DependencyProvider::get_dependencies` to return an iterator instead of
a hashmap to avoid the conversion cost from our dependencies `Vec` to
the pubgrub's hashmap. These changes are difficult to make in pubgrub
since they complicate the public api. But we don't actually use
`DependencyProvider::get_dependencies`, so we rolled those
customizations back in pubgrub-rs/pubgrub#226
and instead opted to change only the internal
`add_incompatibility_from_dependencies` method that we exposed in our
fork. This aligns us closer with upstream, removes the design questions
about `DependencyProvider` from our concerns and reduces our diff (not
counting the github action) to +36 -12.

Bump version to v0.2.6 (astral-sh#3991)

Bump version to v0.2.5 (astral-sh#3885)

Bump version to 0.2.4 (astral-sh#3840)

Bump version to 0.2.3 (astral-sh#3827)

Bump version to 0.2.2 (astral-sh#3774)

Bump version to v0.2.1 (astral-sh#3763)

Remove unused methods from `Resolution` (astral-sh#3754)