v0.21.1.3

⚠️ Removed support for Daint and Tsa!
⚠️ Removed sysconfigs for Balfrin and Tasna!
⚠️ To run spack with an upstream, it needs to be defined when sourcing spack, i.e. . spack-c2sm/setup-env.sh /user-environment

What's Changed

• Remove Tsa by @dominichofer in #983
• remove infero and all dependencies by @jonasjucker in #985
• [balfrin][tasna] Remove sysconfigs by @dominichofer in #984
• Remove Daint by @dominichofer in #987
• drop rttov by @jonasjucker in #986
• Remove execution permission from setup-env.sh by @dominichofer in #991
• Update README.md by @dominichofer in #995

Full Changelog: v0.21.1.2...v0.21.1.3