Bump Cabal-syntax bound to let it work on master branch of cabal

Author: Mikolaj

hackage-repo-tool/hackage-repo-tool.cabal

@@ -90,7 +90,7 @@ executable hackage-repo-tool
     build-depends: network     >= 2.5 && < 2.6
 
   if flag(Cabal-syntax)
-    build-depends: Cabal-syntax >= 3.7 && < 3.9
+    build-depends: Cabal-syntax >= 3.7 && < 3.10
   else
     build-depends: Cabal        >= 1.14    && < 1.26
                              || >= 2.0     && < 2.6