Disable ghc docs by default #2927

Job	Run time
runghc	10s
unit-tests	4s
nix-build	2h 9m 3s
build-extra-hackages	6s
cabal	8s
cabal-doExactConfig	10s
hix	29m 31s
maintainer-scripts	7s
multi-target	1m 2s
plan-extra-hackages	14s
shellFor-hoogle	41s
shellFor-multiple-package	1m 55s
shellFor-not-depends	1m 2s
shellFor-single-package	7m 54s
tests-benchmarks	32s
closure-size	9s
check-materialization-concurrency	24s
docs	59m 48s
hydra-ifdLevel-0-and-1	16m 19s
hydra-ifdLevel-2	16m 5s
hydra-ifdLevel-3	30m 15s
update-docs	9s
check-path-support	13s
haskell-nix-roots-do-not-require-IFDs	45s
hydra-without-remote-builders-ghc9101	1m 30s
hix-cabal	11m 44s
hydra-without-remote-builders-ghc966	2m 35s
nix-tools	28s
	5h 13m 3s

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