databases/redis_exporter: Update 1.80.0 => 1.81.0
Changelog:
https://github.com/oliver006/redis_exporter/releases/tag/v1.81.0
Commit log:
https://github.com/oliver006/redis_exporter/compare/v1.80.0...v1.81.0
Drop ${STRIP} as it's already implied.
PR: 293133