Fix indent to allow copy/paste of sample code to work (#3701)

Author: roy7

docs/source/notebooks/bayesian_neural_network_advi.ipynb

@@ -357,10 +357,10 @@
     "def production_step1():\n",
     "    pm.set_data(new_data={'ann_input': X_test, 'ann_output': Y_test}, model=neural_network)\n",
     "    ppc = pm.sample_posterior_predictive(trace, samples=500, progressbar=False, model=neural_network)\n",
-    "\n",
+    "    \n",
     "    # Use probability of > 0.5 to assume prediction of class 1\n",
     "    pred = ppc['out'].mean(axis=0) > 0.5\n",
-    "    \n",
+    "\n",
     "def production_step2():\n",
     "    sample_proba(X_test, 500).mean(0) > 0.5"
    ]