Update the 2021 Hackage index (`cardano-shell`?) because it sometimes fails on CI

[michalrus]

Context

Sometimes Daedalus fails to build on the Hydra CI, because an ancient Go compiler has some non-determinism in its build, as suspected by @dermetfan.

It probably is caused by very old dependencies of cardano-shell? It’s the launcher that we use to start Daedalus – it’s the first process.

https://github.com/input-output-hk/cardano-shell/blob/5aafc9fc231eecf2e3d59bae1de346cf23227d07/nix/sources.json#L2-L13

See this Slack thread with SREs.

Example

https://github.com/input-output-hk/daedalus/runs/49179806554

https://ci.iog.io/eval/86012#tabs-errors

in job ‘installer.x86_64-linux.mainnet’:
error: derivation 'installer.x86_64-linux.mainnet' does not have valid outputs: error:

[…]

              … while calling the 'import' builtin
                at /nix/store/papr19rm96rwwnkf3qcna5f5hvg274fk-haskell.nix-src/lib/import-and-filter-project.nix:18:13:
                  17|   projectSubDir'' = if projectSubDir == "" then "" else projectSubDir + "/"; # With trailing /
                  18|   project = import "${projectNix}${projectSubDir'}";
                    |             ^
                  19| in project // {

              … while realising the context of path '/nix/store/xwcx0viri3xc07773dsm5yx80xvlqww5-haskell-project-plan-to-nix-pkgs'

              error: 1 dependencies of derivation '/nix/store/bizxsdxqbbr1mi7ki0pswfw4big3qdz2-haskell-project-plan-to-nix-pkgs.drv' failed to build