bump release version to 0.6.8 (kornia#1938)

Update _version.py (kornia#1847)

bump version 0.6.6 (kornia#1791)

release 0.6.5 (kornia#1709)

* grayscale to rgb for torch.uint8

* release 0.6.5

release 0.6.4 (kornia#1643)

* release 0.6.4

* Update CHANGELOG.md

release 0.6.3 (kornia#1550)

* release 0.6.3

* Update CHANGELOG.md

release 0.6.2 (kornia#1478)

* release 0.6.2

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update CHANGELOG.md

* Update CHANGELOG.md

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

hotfix: remove mutable object in constructor (kornia#1423)

* hotfix: remove mutable object in constructor

* Apply Luis suggestions

* Update integrated.py

Co-authored-by: Dmytro Mishkin <[email protected]>

Update image_stitching.rst

hotfix with pad