Remove OpenSocial references

The OpenSocial addon has been removed a long time ago.

Remove the params from the nuxeo.conf config file:
https://github.com/nuxeo/nuxeo/blob/master/nuxeo-distribution/nuxeo-server-tomcat/src/main/resources/tomcat/bin/nuxeo.conf#L147

Check if any other files or code reference OpenSocial.