haskellPackages.idris: Fix build (new GHC 8.8 & old megaparsec 7)

The hackage-packages.nix change was generated by hackage2nix v2.15.1 from Hackage revision
https://github.com/commercialhaskell/all-cabal-hashes/commit/ad4a70d448051948f2064d0bba5e63eab25f04d8.

pkgs/development/haskell-modules/hackage-packages.nix

@@ -137052,8 +137052,6 @@ self: {
        ];
        description = "Functional Programming Language with Dependent Types";
        license = stdenv.lib.licenses.bsd3;
-       hydraPlatforms = stdenv.lib.platforms.none;
-       broken = true;
      }) {inherit (pkgs) gmp;};
 
   "ieee" = callPackage
@@ -162376,6 +162374,27 @@ self: {
        broken = true;
      }) {};
 
+  "megaparsec_7_0_5" = callPackage
+    ({ mkDerivation, base, bytestring, case-insensitive, containers
+     , criterion, deepseq, mtl, parser-combinators, scientific, text
+     , transformers, weigh
+     }:
+     mkDerivation {
+       pname = "megaparsec";
+       version = "7.0.5";
+       sha256 = "0bqx1icbmk8s7wmbcdzsgnlh607c7kzg8l80cp02dxr5valjxp7j";
+       libraryHaskellDepends = [
+         base bytestring case-insensitive containers deepseq mtl
+         parser-combinators scientific text transformers
+       ];
+       benchmarkHaskellDepends = [
+         base containers criterion deepseq text weigh
+       ];
+       description = "Monadic parser combinators";
+       license = stdenv.lib.licenses.bsd2;
+       hydraPlatforms = stdenv.lib.platforms.none;
+     }) {};
+
   "megaparsec" = callPackage
     ({ mkDerivation, base, bytestring, case-insensitive, containers
      , criterion, deepseq, mtl, parser-combinators, scientific, text