babashka: increase java heap space max to 4500

3g has very long build times and also doesn't build 100% of the time
it's also the new default since:
7fc33dcb21

pkgs/development/interpreters/clojure/babashka.nix

@@ -42,7 +42,7 @@ stdenv.mkDerivation rec {
       --no-server \
       --report-unsupported-elements-at-runtime \
       "--initialize-at-run-time=org.postgresql.sspi.SSPIClient" \
-      "-J-Xmx3g"
+      "-J-Xmx4500m"
   '';
 
   installPhase = ''