CONTRIBUTING: update Lima guide

[AkihiroSuda]

The new form might be easier to use.
The old form is still valid.

• 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 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 brew install --build-from-source <formula>)? If this is a new formula, does it pass brew audit --new <formula>?

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[SMillerDev]

It says

If you don't have Docker installed:

Would docker context use lima still work in that case?

[AkihiroSuda]

It says

If you don't have Docker installed:

Would docker context use lima still work in that case?

Yes, because we are installing docker (CLI) formula in the guide.

[MikeMcQuaid]

Thanks @AkihiroSuda!