timetrap: update to ruby 3.4 to fix missing extensions warnings

this is the same fix as in 11da150d8ee7f8bcd97e25bd448612c36245453f
for another ruby program. see discussion in #400243.

pkgs/by-name/ti/timetrap/package.nix

···
 {
   stdenv,
   lib,
+  ruby_3_4,
   bundlerEnv,
   bundlerApp,
   bundlerUpdateScript,
···
 }:
 
 let
-  ttBundlerApp = bundlerApp {
+  ttBundlerApp = (bundlerApp.override { ruby = ruby_3_4; }) {
     pname = "timetrap";
     gemdir = ./.;
     exes = [
···
     passthru.updateScript = bundlerUpdateScript "timetrap";
   };
 
-  ttGem = bundlerEnv {
+  ttGem = (bundlerEnv.override { ruby = ruby_3_4; }) {
     pname = "timetrap";
     gemdir = ./.;
   };