Use ruby that supports jemalloc

In production, memory usage of the server can be steadily increased by
performing an activestorage request in an infinite loop. The issue can be
reproduced in development (though it is less pronounced)

When using a ruby configured with jemalloc, the issue is no longer reproducible
in development. So I'm hoping that the same will be true in production.

flake.nix

@@ -16,7 +16,7 @@
         pkgs = import nixpkgs { inherit system; overlays = [ devshell.overlays.default ]; };
         gems = pkgs.bundlerEnv rec {
           name = "accentor-api-env";
-          ruby = pkgs.ruby_3_3;
+          ruby = pkgs.ruby_3_3.override { jemallocSupport = true; };
           gemfile = ./Gemfile;
           lockfile = ./Gemfile.lock;
           gemset = ./gemset.nix;