[TASK] Deprecate AbstractPlugin pi_list_searchBox

Old-old search content element could be used in frontend with
AbstractPlugin method pi_list_searchBox(). Rendered output is
hopelessly outdated, method is deprecated now.

Resolves: #62854
Releases: master
Change-Id: Ie3478333b0a8b16835c2074e70c2a9643acc388a
Reviewed-on: http://review.typo3.org/34286


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Felix Kopp <felix-source@phorax.com>
Tested-by: Felix Kopp <felix-source@phorax.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>