stdenv: deprecate unused adapters
stdenv: deprecate unused adapters

stdenv: deprecate addCoverageInstrumentation adapter

this used to be used in nixos/tests but it hasn't been used in nixpkgs
for years

stdenv: deprecate replaceMaintainersField adapter

it was added in 2009 in 01e98e49b155d989d8c80066db6de910396cdcaa
by nbp
there are no uses of it in nixpkgs now

stdenv: deprecate validateLicenses adapter

it was added in 2009 in b29073af25cb0ff2d8d9a0aa1f958316904d3dc9

unfreePredicate is now handled in ./pkgs/stdenv/generic/check-meta.nix
so this is unnecessary

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