Add missing params to `groups_details_updated` action

[christianwach]

The hook signature of the groups_details_updated action has changed in BuddyPress 2.2.0. Two new params added, see: https://buddypress.trac.wordpress.org/changeset/9204

This PR adds default values that prevent bp_groups_group_details_updated_add_activity() from throwing a "missing parameters" error. Also copies in the docblock for the hook for reference.

[boonebgorges]

Good catch. It seems to me that we should not be using this hook here at all. It's a BP core hook. We should be using 'groupblog_details_updated'. I think it's probably a typo that it's like this at all. What do you think?

[christianwach]

Hmm, good point. I thought it might be called to bust the group caches. Seems like an obscure way of doing so, if it is indeed necessary. I'd tend to agree with changing it to groupblog_details_updated and do cache-busting (if needed) explicitly.

[boonebgorges]

It's possible that removing this hook will break something somewhere, but the chances are pretty remote, and YOLO

[christianwach]

Closed in favour of 7902c49caa12b030151ff453453ddc13dbee2711. Thanks for attending to this, Boone.