Update the description of the max-lag-millis in docs

[dontstopbelieveing]

A Pull Request should be associated with an Issue.

We wish to have discussions in Issues. A single issue may be targeted by multiple PRs.
If you're offering a new feature or fixing anything, we'd like to know beforehand in Issues,
and potentially we'll be able to point development in a particular direction.

Related issue: #1387

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Description

This PR updates the docs for the description of the max-lag-millis command line parameter, specially in context of running on master

In case this PR introduced Go code changes:

• contributed code is using same conventions as original code
• script/cibuild returns with no formatting errors, build errors or unit test errors.

[dontstopbelieveing]

@meiji163 @timvaillancourt @rashiq Can I please request a review?

[timvaillancourt]

LGTM, thanks @dontstopbelieveing 🙏