[web/views/formrenderer] do not use `cubicweb:target` attribute on form (closes #5534074)
The `cubicweb:target` is a flag indicating that the form data (with
file input) shall be posted inside an iframe - this is a well known
"ajax-like" workaround to post files with browsers that do not support
`FormData` (a.k.a IE<10).
The `cubicweb:target` was introduced when CW used the "xhtml strict"
doctype. Now that CW uses the "html5" doctype, this namespaced
attribute is no longer necessary and the iframe can be generated
directly.
Before this patch, CW inserts the `cubicweb:target` attribute in the
form DOM element (server side) and `setFormsTarget()` updates the
DOM with a new `<iframe>` element (client side).
Now, CW inserts the `<iframe>` DOM element directly (server side),
making `setFormsTarget` useless.
addressbook
basket
blog
book
calendar
comment
company
email
file
folder
i18ncontent
keyword
link
mailinglist
person
tag
timeseries
vcsfile