Update nix maven hash (#4796)

The nix derivation for k started failing due to a hash mismatch in the
maven nix derivation. This is probably due to maven dependencies being
changed upstream, outside of our control. This happened for the first
time last week, see
[here](22d49bc),
and has now occurred a second time.

Currently this issue is blocking other pull requests due to [failing
CI](https://github.com/runtimeverification/k/actions/runs/14641493584/job/41098410643?pr=4782#step:6:10121).

I'll investigate this further and post updates of the investigation here
or create an issue. I'd be a problem if this starts happening more
frequently instead of only once.

Author: juliankuners

flake.nix

@@ -84,7 +84,7 @@
 
             mk-k-framework = { haskell-backend-bins, llvm-kompile-libs }:
               prev.callPackage ./nix/k.nix {
-                mvnHash = "sha256-uHhx3L2ma9/N5fbagpXMbE3boL7RNfkRy5vzPmKOfU8=";
+                mvnHash = "sha256-v/6tVTx3UgIn95r1KUeYTRbLnDlaNI/B9+g8NSPDx34=";
                 manualMvnArtifacts = [
                   "org.scala-lang:scala-compiler:2.13.13"
                   "ant-contrib:ant-contrib:1.0b3"