Remove social_user update hooks pre-10.0.0

Problem/Motivation

We never support skipping major versions of Open Social, so for Open Social 11 we could already remove all update hooks from before Open Social 10. We've missed the 11.0 release but can still do the same for 12.0, we can clean up the 10.x specific hooks in a future commit to give ourselves a bit of breathing room.

Steps to reproduce

Proposed resolution

Remove all pre-10.0 update hooks.

Remaining tasks

User interface changes

API changes

Data model changes