fix(form): stop passing deprecated $message to V3 variables in validate()

[TDannhauer]

Summary

• Fixes log spam when legacy Horde_Form validates forms that use V3 variables created by Horde_Form::createVariable().
• Horde_Form::validate() no longer passes the deprecated second $message argument to V3 BaseVariable instances; it is still passed for legacy Horde_Form_Variable wrappers (e.g. app-specific types without a V3 class).
• Aligns legacy form validation with Horde\Form\V3\BaseForm::validate(), which already calls $var->validate($vars) with a single argument.

Problem

Horde_Form::createVariable() now returns V3 variables (e.g. Horde\Form\V3\TextVariable) when a modern class exists. Legacy Horde_Form::validate() still called:

[TDannhauer]

pls review whether this approach is viable @ralflang .

turba floods the logs with this issue

[amulet1]

We should really finish migration to V3 in other apps first.

[TDannhauer]

I am open for every approach, but leaving it as it is is not viable imo as turba is flooding logs. stants not stable code

[ralflang]

See also horde/imp#48 log output.