You cannot remove Update Rollup 5. Specific database updates are applied in Update Rollup5 that will not let you uninstall Update Rollup 5. You should back up your databases before you install this update.
Dynamics CRM Q4 Service Update
Update Rollup 5 also contains the Dynamics CRM Q4 Service Update features. For more information about the Dynamics CRM Q4 Service Update features, visit the following Microsoft website:
Microsoft Dynamics CRM Activity Feeds provide real time notifications and quick sharing of information that the team cares about via quick and short updates. Activity Feeds enable a user to follow and listen in on important activities that take place around the people, accounts, contacts, leads, opportunities or anything else that they care about.