mongodb-atlas-cli, nim: add conflicts_with

[chenrui333]

• Have you followed the guidelines for contributing?
• Have you ensured that your commits follow the commit style guide?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with HOMEBREW_NO_INSTALL_FROM_API=1 brew install --build-from-source <formula>, where <formula> is the name of the formula you're submitting?
• Is your test running fine brew test <formula>, where <formula> is the name of the formula you're submitting?
• Does your build pass brew audit --strict <formula> (after doing HOMEBREW_NO_INSTALL_FROM_API=1 brew install --build-from-source <formula>)? If this is a new formula, does it pass brew audit --new <formula>?

---

$ tree /opt/homebrew/Cellar/nim/2.0.2/
...
├── nim
│   ├── bin
│   │   ├── atlas
│   │   ├── nim
│   │   ├── nimble
│   │   ├── nimgrep
│   │   ├── nimpretty
│   │   ├── nimsuggest
│   │   └── testament

$ tree /opt/homebrew/Cellar/mongodb-atlas-cli/1.16.0/
...
├── bin
│   └── atlas

found while testing #165382