Merge pull request optuna#2975 from HideakiImamura/bump-up-version-2.10

Bump up version to 2.10

Merge pull request optuna#2839 from hvy/bump-to-v2.9.1

Bump to v2.9.1

Merge pull request optuna#2828 from hvy/bump-to-v2.9.0

Bump to v2.9.0

Merge pull request optuna#2728 from hvy/gp-2717

Backport of optuna#2717

Merge pull request optuna#2566 from HideakiImamura/release-v2.7.0

Bump up version to v2.7.0

Merge pull request optuna#2445 from hvy/bump-version-260

Bump `release-v2.6.0` version `2.6.0`

Merge pull request optuna#2282 from HideakiImamura/bump-up-v2.5.0

Bump up version number to v2.5.0

Merge pull request optuna#2188 from HideakiImamura/2187-backport

[Backport] Fix the syntax of `pypi-publish.yml`

Merge pull request optuna#1978 from toshihikoyanase/add-rdb-support-t…

…o-motpe

Add RDB support to `MoTPEMultiObjectiveSampler`

Merge pull request optuna#1886 from hvy/bump-to-v2.2.0

Bump to v2.2.0