AbstractBlock::getPermissionsError is never called (https://codesearch.wmcloud.org/search/?q=getPermissionsError&i=nope&files=&excludeFiles=&repos=) and after T317204 it will never be used.
Acceptance criteria
- AbstractBlock::getPermissionsError is hard deprecated: its deprecation is documented, and calling it emits deprecation warnings
Notes
Documentation on the deprecation process: https://www.mediawiki.org/wiki/Stable_interface_policy#Deprecation_process
Example of hard deprecating method: https://gerrit.wikimedia.org/r/c/mediawiki/core/+/812549