Contact Form: Disable comment forms from displaying on dynamic confirmation pages

### Impacted plugin

Jetpack

### What

With a Contact Form block added to a site, once a message has been submitted a comment form displays beneath the message confirmation (if comments are enabled on the site).

Since this is a dynamically generated page, it would make sense to hide the comment form if possible. This may be theme dependant in some cases but I noticed it with Twenty Twenty Three (beta), Twenty Twenty Two, Twenty Twenty.

An example of how the confirmation page currently looks:

Suggested in internal testing: p8oabR-Ym-p2#comment-6735

Reproduce the issue with a Jetpack Contact Form block and comments enabled, checking the Twenty Twenty, Twenty Twenty-Two, and Twenty Twenty-Three themes named in the report. Done means the dynamically generated confirmation page shows the message without a comment form while regular pages retain their expected comment behavior.

Written by the indexing model from the issue text.