Disable executable build in cabal

Until something like haskell/cabal#4660 happens or we end up on a nixpkgs with the version we want in it.

servant-auth-server/servant-auth-server.cabal

@@ -68,24 +68,24 @@ library
       Servant.Auth.Server.SetCookieOrphan
   default-language: Haskell2010
 
-executable readme
-  main-is: README.lhs
-  hs-source-dirs:
-      executables
-  default-extensions: AutoDeriveTypeable ConstraintKinds DataKinds DefaultSignatures DeriveFoldable DeriveFunctor DeriveGeneric DeriveTraversable FlexibleContexts FlexibleInstances FunctionalDependencies GADTs KindSignatures MultiParamTypeClasses OverloadedStrings RankNTypes ScopedTypeVariables TypeFamilies TypeOperators
-  ghc-options: -Wall -pgmL markdown-unlit
-  build-tool-depends: markdown-unlit:markdown-unlit
-  build-depends:
-      base
-    , servant-auth
-    , servant-auth-server
-    , servant-server
-    , aeson
-    , mtl
-    , warp
-    , transformers
-    , markdown-unlit
-  default-language: Haskell2010
+--executable readme
+--  main-is: README.lhs
+--  hs-source-dirs:
+--      executables
+--  default-extensions: AutoDeriveTypeable ConstraintKinds DataKinds DefaultSignatures DeriveFoldable DeriveFunctor DeriveGeneric DeriveTraversable FlexibleContexts FlexibleInstances FunctionalDependencies GADTs KindSignatures MultiParamTypeClasses OverloadedStrings RankNTypes ScopedTypeVariables TypeFamilies TypeOperators
+--  ghc-options: -Wall -pgmL markdown-unlit
+--  build-tool-depends: markdown-unlit:markdown-unlit
+--  build-depends:
+--      base
+--    , servant-auth
+--    , servant-auth-server
+--    , servant-server
+--    , aeson
+--    , mtl
+--    , warp
+--    , transformers
+--    , markdown-unlit
+--  default-language: Haskell2010
 
 test-suite spec
   type: exitcode-stdio-1.0