Revert "enclose in square brackets"

[BobDotCom]

Summary

Reverts #1435, as it is incorrect.
Ref: https://docs.python.org/3/library/typing.html?highlight=concatenate#typing.Concatenate

Information

• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed).
• This PR is not a code change (e.g. documentation, README, typehinting, examples, ...).

Checklist

• I have searched the open pull requests for duplicates.
• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why.

[BobDotCom]

Fix typo