[tutorials] Move Multibody to the top of the index page (#17555)

* [tutorials] Move Multibody to the top of the index page

For many new users it will be a more graceful starting point than our
mathematical optimization toolbox.

tutorials/index.ipynb

@@ -12,6 +12,15 @@
     "For an overview about the philosophy behind [Drake](https://drake.mit.edu), consider reading this [blog post](https://medium.com/toyotaresearch/drake-model-based-design-in-the-age-of-robotics-and-machine-learning-59938c985515).\n",
     "We have organized the tutorials around the three major components described in that post:\n",
     "\n",
+    "## Multibody Dynamics\n",
+    "\n",
+    "- [Authoring a multibody simulation](./authoring_multibody_simulation.ipynb)\n",
+    "- [Mathematical programming with MultibodyPlant](./mathematical_program_multibody_plant.ipynb)\n",
+    "- [PyPlot animation](./pyplot_animation_multibody_plant.ipynb)\n",
+    "- [Rendering MultibodyPlant](./rendering_multibody_plant.ipynb)\n",
+    "\n",
+    "More multibody tutorials coming soon!\n",
+    "\n",
     "## Mathematical Programming\n",
     "\n",
     "- [MathematicalProgram](./mathematical_program.ipynb)\n",
@@ -24,15 +33,6 @@
     "- [Sum-of-squares optimization](./sum_of_squares_optimization.ipynb)\n",
     "- [Enabling licensed solvers on Deepnote](./licensed_solvers_deepnote.ipynb)\n",
     "\n",
-    "## Multibody Dynamics\n",
-    "\n",
-    "- [Authoring a multibody simulation](./authoring_multibody_simulation.ipynb)\n",
-    "- [Mathematical programming with MultibodyPlant](./mathematical_program_multibody_plant.ipynb)\n",
-    "- [PyPlot animation](./pyplot_animation_multibody_plant.ipynb)\n",
-    "- [Rendering MultibodyPlant](./rendering_multibody_plant.ipynb)\n",
-    "\n",
-    "More multibody tutorials coming soon!\n",
-    "\n",
     "## Dynamical Systems\n",
     "\n",
     "- [Modeling Dynamical Systems](./dynamical_systems.ipynb)\n",