docs: clarify CLI autoConnect support

[MukundaKatta]

Summary:

• document that chrome-devtools start intentionally does not support --autoConnect
• point users to --browserUrl as the supported way to attach the CLI daemon to an existing Chrome instance

Testing:

• reviewed docs diff locally

Relates to #1184

[Lightning00Blade]

Thanks for the PR but we are going to enable support once #1859 lands, so this PR will be obsolete.