remove relic data

src/Lib/Registry.hs

@@ -16,7 +16,6 @@ import           Yesod.Core
 
 import           Lib.Semver
 import           Lib.Types.Semver
-import           Data.Char
 
 type Registry = HashMap String (HashMap AppVersion FilePath)
 
@@ -51,11 +50,6 @@ type S9PK = Extension "s9pk"
 type SYS_EXTENSIONLESS = Extension ""
 type PNG = Extension "png"
 
-data Extensions = S9PK | PNG | EMPTY
-    deriving (Read)
-instance Show Extensions where
-    show a = fmap toLower $ show a
-
 instance IsString (Extension a) where
     fromString = Extension