Fix a bug in IsString instance of FieldSettings

yesod-form/Yesod/Form/Types.hs

@@ -102,7 +102,7 @@ data FieldSettings master = FieldSettings
     , fsAttrs :: [(Text, Text)]
     }
 
-instance (a ~ Text) => IsString (FieldSettings a) where
+instance IsString (FieldSettings a) where
     fromString s = FieldSettings (fromString s) Nothing Nothing Nothing []
 
 data FieldView sub master = FieldView

yesod-form/hello-forms.hs

@@ -39,8 +39,7 @@ data HelloForms = HelloForms
 instance RenderMessage HelloForms FormMessage where
     renderMessage _ _ = defaultFormMessage
 
-instance Yesod HelloForms where
-    approot _ = ""
+instance Yesod HelloForms
 
 fixType :: Handler a -> Handler a
 fixType = id