Fix mypy errors attributed to pytorch_lightning.trainer.callback_hook.py

[jxtngx]

What does this PR do?

Fix mypy errors attributed to pytorch_lightning.trainer.callback_hook.py for issue #13445

Does your PR introduce any breaking changes? If yes, please list them.

Before submitting

• Was this discussed/approved via a GitHub issue? (not for typos and docs)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests? (not for typos and docs)
• Did you verify new and existing tests pass locally with your changes?
• Did you list all the breaking changes introduced by this pull request?
• Did you update the CHANGELOG? (not for typos, docs, test updates, or minor internal changes/refactors)

PR review

Anyone in the community is welcome to review the PR.
Before you start reviewing, make sure you have read the review guidelines. In short, see the following bullet-list:

• Is this pull request ready for review? (if not, please submit in draft mode)
• Check that all items from Before submitting are resolved
• Make sure the title is self-explanatory and the description concisely explains the PR
• Add labels and milestones (and optionally projects) to the PR so it can be classified

Did you have fun?

Make sure you had fun coding 🙃

[jxtngx]

@otaj @carmocca @rohitgr7

the class in this module is deprecated and will be removed in 1.8; should I still work this PR?

[carmocca]

the class in this module is deprecated and will be removed in 1.8; should I still work this PR?

I suggest dropping this. However, you will be able to open a PR removing it the next week (after the 1.7 release) :)

[jxtngx]

Closed given callback_hook will be removed after 1.7 release. Will follow up with new PR to remove.