Make version 0.1.1.1 compile with ghc-9.8

The `plutus-core` package currently has:
```
    , dependent-sum               >=0.7.1.0
    , dependent-sum-template      <0.1.2
```
This commit takes the commit that was tagged as version 0.1.1.1 and
fixes it for ghc-9.8.

See: obsidiansystems#9

src/Data/Dependent/Sum/TH/Internal.hs

@@ -28,7 +28,13 @@ classHeadToParams t = (h, reverse reversedParams)
 deriveForDec :: Name -> (Q Type -> Q Type) -> ([TyVarBndrSpec] -> [Con] -> Q Dec) -> Dec -> Q [Dec]
 deriveForDec className makeClassHead f dec = deriveForDec' className makeClassHead (f . changeTVFlags specifiedSpec) dec
 
-deriveForDec' :: Name -> (Q Type -> Q Type) -> ([TyVarBndrUnit] -> [Con] -> Q Dec) -> Dec -> Q [Dec]
+deriveForDec' :: Name -> (Q Type -> Q Type)
+#if __GLASGOW_HASKELL__ >= 908
+  -> ([TyVarBndr BndrVis] -> [Con] -> Q Dec)
+#else
+  -> ([TyVarBndrUnit] -> [Con] -> Q Dec)
+#endif
+  -> Dec -> Q [Dec]
 deriveForDec' className _ f (InstanceD overlaps cxt classHead decs) = do
     let (givenClassName, firstParam : _) = classHeadToParams classHead
     when (givenClassName /= className) $