pythonPackages.flask_cache: remove
pythonPackages.flask_cache: remove

The package is currently broken and most folks recommend to use
`flask-caching` (see
https://github.com/thadeusb/flask-cache/issues/171).

The only package in `nixpkgs` which remained to use `flask_cache`
(`graphite_api`) still builds with `pythonPackages.flask-caching`.

The removal and corresponding `graphite_api` change unbreaks several
Hydra builds (see https://hydra.nixos.org/build/76953777).

NixOS/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs