Agda: package builds fine these days

Tested with 8.0.2 and 8.2.1.

pkgs/development/haskell-modules/configuration-common.nix

···
     sha256 = "1vss7b99zrhw3r29krl1b60r4qk0m2mpwmrz8q8zdxrh33hb8pd7";
   });
 
-  # happy 1.19.6+ broke the Agda build. Sticking with the previous version
-  # avoided that issue, but now the build fails with a segmentation fault
-  # during the install phase for no apparent reason:
-  # https://hydra.nixos.org/build/60678124
-  Agda = markBroken (super.Agda.override { happy = self.happy_1_19_5; });
-
   # cryptol-2.5.0 doesn't want happy 1.19.6+.
   cryptol = super.cryptol.override { happy = self.happy_1_19_5; };