base: fix misc index stemming language in demosite
base: fix misc index stemming language in demosite

* Sets english as stemming language for demosite miscellaneous index.

Signed-off-by: Grzegorz Szpura <900c4f131187ed2a7cfcf1f0200fa0b9c64b7780@cern.ch>
Reviewed-by: Jiri Kuncar <2bdffcb416fed3002465740d19a053a39918cbe5@cern.ch>

tiborsimko/invenio-base,inveniosoftware/invenio-base,inveniosoftware/invenio-base,tiborsimko/invenio-base