chore(eslint): fix errors

[LeoAnesi]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[x] Other... Please describe: While working on another PR to allow connection name in forRoot I saw that the lint command was broken and once fixed I saw errors that weren't related to my code, this PR fix those issues. 

Other information

I ignored @typescript-eslint/ban-types for Function type because it looks difficult to fix, but maybe a better option would have been to put eslint-ignores in current uses to prevent future additions of Function, tell me if so I'll change it.

[LeoAnesi]

The reason : https://github.com/prettier/eslint-config-prettier/blob/main/CHANGELOG.md#version-800-2021-02-21

[kamilmysliwiec]

LGTM