python3Packages.jax: add GaetanLepage to maintainers

pkgs/development/python-modules/jax/default.nix

···
     description = "Source-built JAX frontend: differentiate, compile, and transform Numpy code";
     homepage = "https://github.com/google/jax";
     license = lib.licenses.asl20;
-    maintainers = with lib.maintainers; [ samuela ];
+    maintainers = with lib.maintainers; [
+      GaetanLepage
+      samuela
+    ];
   };
 }