Release of v2.21.0

Bump version to v2.20.0

Bump version to v2.20.0

[Fix] Cancel previous runs that are not completed (open-mmlab#6772)

* [Fix] Cancel previous runs that are not completed

* Empty to check

* Empty to check

Support circleci (open-mmlab#6630)

* add ci

* rename

* fix mmtrack unittest

* update mmcv version

bump version to v2.18.1 (open-mmlab#6510)

* bump version to v2.18.1

* Update changelog.md

Bump version to v2.18.0 (open-mmlab#6365)

* Bump version to v2.18.0

* update

* update

* Update changelog.md

* update

* resolve comments

* Update compatibility.md

Bump version to v2.17.0 (open-mmlab#6152)

Bump version to v2.16.0 (open-mmlab#5971)

* try to install cuda

* use 1804

* bump version

bump version to 2.15.1 (open-mmlab#5857)

* bump version to 2.15.1

* update versions

* make en/cn consistency

[Fix]: fix panoptic dependency issue when publishing to pypi (open-mm…

…lab#5781)

* fix panoptic dependency issue when publish to pypi

* resolve comments