Update main entry-point docs to use lowercase `args`

[mbauman]

I would like to suggest a change to the doc to recommend users define main as main(args) instead of main(ARGS) to clarify the differences between the global var Core.ARGS and the function parameter. Defining the main(ARGS) is confusing to me if the ARGS is just a normal parameter.

Originally posted by @ctarn in #50974 (comment)

[ctarn]

It would be great if we could finish it before the release of 1.11.0. I am also happy to prepare a PR if needed. I can start it tomorrow since I'm struggling with a report due in 12 hours later...

[mbauman]

That'd be great — go for it! I just didn't want your comment to get lost.