xmlns:svg is an XML namespace declaration that would be valid in XHTML
but not in HTML. Even in XHTML, it wouldn’t be necessary because we
don’t write SVG tags prefixed like <svg:circle>, only unprefixed like
<circle>.
Signed-off-by: Anders Kaseorg <andersk@mit.edu>
This should make it easier to find the templates that are actually
part of the core webapp, instead of having them all mixed together
with the portico pages.