Forms: date field - make the (YYYY-DD-MM) text on date label optional

### Impacted plugin

Jetpack

### What

Make it possible to remove the `YYYY-DD-MM` as part of the date field label in Jetpack forms

### How

User requesting that this part of the label be optional.

https://wordpress.org/support/topic/how-to-remove-date-pattern-text-from-label-of-date-fields/

Should this be a toggle under settings "Show date format" or simply something we append in label by default but allow users to just edit it out? Or will we need this at all if we update to better UI library?

No files, tests, or entry points are identified in the issue. Start by locating the Jetpack forms date-field label implementation and its current settings, then clarify with maintainers whether the date format should be controlled by a toggle or editable label before defining the expected behavior.

Written by the indexing model from the issue text.