Update media.txt

Fixed typo: froms -> forms
Merge pull request #1256 from krmboya/patch-1

Fixed #20575 -- Typo in docs/topics/forms/media.txt
Fixed #20567 - Documented BoundField.id_for_label.

Thanks littlepig for the suggestion.
Fixed #19875 - Added warnings regarding DEBUG=False and empty ALLOWED_HOSTS
Added runserver validation to detect if DEBUG=False and ALLOWED_HOSTS is empty.

Refs #19875.