databases/redis_exporter: Update to 1.0.3

While I'm here:

• Add path to license file.
• Pet portclippy by grouping related variables together (USE_ and GO_).

Changelog:

https://github.com/oliver006/redis_exporter/releases/tag/v1.0.3

PR: 238823
Submitted by: Volodymyr Kostyrko <arcade@b1t.name> (maintainer)