LPS-48100 Remove bootstrap grid classes from form-search

Ticket: [LPS-48100](https://issues.liferay.com/browse/LPS-48100)

The following files did contain bootstrap `col-xs-12` classes, but removing them caused minor UI bugs (see ticket attachments):

* `html/portlet/document_library/toolbar.jsp`
* `html/portlet/document_library/top_links.jsp`