Show warning message about media types assignment only for bulk upload with multiple media types

Problem/Motivation

The module provides this warning message:

Please be aware that if file extensions overlap between the media types that are
available in this upload form, that the media entity will be assigned
automatically to one of these types.

Imho this only makes sense if there are more than one media types configured for the bulk upload form. So if only one media type is configured it would be better to not show this warning, since it may confuse the user.

Steps to reproduce

Configure bulk upload form with only one media type
See the warning message that is designed for multitple media types only

Proposed resolution

check for configured media types
if only one, do not show the warning

Remaining tasks

patch

User interface changes

warning message only for form with multiple media types configured

API changes

none

Data model changes