[web/test] stop calling loadxhtml with a form.callback
It was deprecated in 3.9 (changeset 7b9553a9db65) and removed in 3.18.
Related to #5533303.
Schema of the data
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First take a look at the data schema_ then try to remember that you are browsing
through a heap of data by applying stylesheets to the results of queries. This
site is not a content management system with items placed in folders. It is an
interface to a database which applies a view to retreived data.
.. _schema: ../schema