install: remove oauthlib from devel dependencies
install: remove oauthlib from devel dependencies

* Fixes devel build by removing oauthlib from devel dependencies.
  This is due to an incompatibility between flask-oauthlib and
  oauthlib (see lepture/flask-oauthlib#335)

Signed-off-by: Nicolas Harraudeau <b43b76f088452fbd97430e599a370977191b854c@cern.ch>

inveniosoftware/invenio-oauth2server,tiborsimko/invenio-oauth2server,tiborsimko/invenio-oauth2server,inveniosoftware/invenio-oauth2server,inveniosoftware/invenio-oauth2server,tiborsimko/invenio-oauth2server