Adapt kore-integration-tests dev shell to new name (#4527)

The name change from `k-framework` to `mk-k-framework` was incomplete,
the `kore-integration-test` dev shell did not work any more. This shell
is used for the Haskell Backend integration tests.
I have tested that [the change here makes the integration test shell
work
again](runtimeverification/haskell-backend@de1cc7d).
Merging this will unblock the [dependency upgrade PR in Haskell
Backend](runtimeverification/haskell-backend#3965).

flake.nix

@@ -210,7 +210,7 @@
             };
         };
         defaultPackage = packages.k;
-        devShells.kore-integration-tests = pkgs.kore-tests (pkgs.k-framework {
+        devShells.kore-integration-tests = pkgs.kore-tests (pkgs.mk-k-framework {
           inherit (pkgs) haskell-backend-bins;
           llvm-kompile-libs = { };
         });