EZP-22133: sudo not working with lazy repository

See [comment in EZP-22133](https://jira.ez.no/browse/EZP-22133?focusedCommentId=87404&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-87404).

Removed `final` keyword on `sudo()` function in core Repository class.
To be *proxy-able*, public functions must be extendable. `final` keyword prevents that.