Fix branch description and standardize URL scheme for lts/ghc-9.10.x
Summary
- Update description from "lts/ghc-0.7.0.x" to "lts/ghc-9.10.x"
- Change horizon-flake-parts URL from http:// to https://
This fixes two inconsistencies identified in the branch audit:
- Incorrect branch description
- Non-standard URL scheme (http instead of https)