providers: typo fix
providers: typo fix

Signed-off-by: Orestis Melkonian <a8803610f79fcd815ba94c447e9ee72ed88af885@gmail.com>

inveniosoftware/invenio-pidstore,inveniosoftware/invenio-pidstore,tiborsimko/invenio-pidstore,tiborsimko/invenio-pidstore