Update nixpkgs pins #3420

Job	Run time
unit-tests	50s
nix-build	7m 37s
tests-benchmarks	1h 6m 4s
runghc	1h 11m 52s
cabal-doExactConfig	1h 11m 54s
multi-target	3m 9s
shellFor-single-package	10m 20s
maintainer-scripts	16s
build-extra-hackages	26s
shellFor-multiple-package	1h 15m 13s
shellFor-not-depends	37s
cabal	22s
plan-extra-hackages	15s
shellFor-hoogle	25s
update-docs	12s
hydra-without-remote-builders-ghc967	1m 19s
haskell-nix-roots-do-not-require-IFDs	38s
hix-cabal	8m 38s
hydra-ifdLevel-2	20m 17s
docs	2m 4s
hydra-ifdLevel-0-and-1	12m 46s
closure-size	10s
check-path-support	23s
check-nix-tools	30s
check-materialization-concurrency	24s
hydra-without-remote-builders-ghc9102	12s
hydra-ifdLevel-3	30m 17s
hix	1m 10s
	6h 28m 20s

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