Fix syntax errors in Ray Tune example pbt_ppo_example.ipynb (#51626)

Just a missing comma and equal sign

Signed-off-by: Jonathan Dumaine <jonathan@dumstruck.com>

Author: JonDum

doc/source/tune/examples/pbt_ppo_example.ipynb

@@ -100,12 +100,12 @@
     "            # These params are tuned from a fixed starting value.\n",
     "            kl_coeff=1.0,\n",
     "            lambda_=0.95,\n",
-    "            clip_param=0.2\n",
+    "            clip_param=0.2,\n",
     "            lr=1e-4,\n",
     "            # These params start off randomly drawn from a set.\n",
     "            num_epochs=tune.choice([10, 20, 30]),\n",
     "            minibatch_size=tune.choice([128, 512, 2048]),\n",
-    "            train_batch_size_per_learner: tune.choice([10000, 20000, 40000]),\n",
+    "            train_batch_size_per_learner=tune.choice([10000, 20000, 40000]),\n",
     "        )\n",
     "        .rl_module(\n",
     "            model_config=DefaultModelConfig(free_log_std=True),\n",