Widen template-haskell version constraint to allow version 2.19

This allows freer-simple to be used with GHC 9.4.X. Prior versions
of template-haskell are not compatible with GHC 9.4. The 2.19 release
of template-haskell seems to be fully compatible with freer-simple.
That is, tests still pass and I haven't noticed any issues in my
own project (which use freer-simple).

Fixes #40

Author: nmeum

freer-simple.cabal

@@ -84,7 +84,7 @@ library
   build-depends:
     , natural-transformation >= 0.2
     , transformers-base
-    , template-haskell >= 2.11 && < 2.19
+    , template-haskell >= 2.11 && < 2.20
 
 executable freer-simple-examples
   import: common