Remove unused theano import

Author: thomasaarholt

Diff for: Chapter1_Introduction/Ch1_Introduction_PyMC3.ipynb

@@ -650,7 +650,6 @@
    ],
    "source": [
     "import pymc3 as pm\n",
-    "import theano.tensor as tt\n",
     "\n",
     "with pm.Model() as model:\n",
     "    alpha = 1.0/count_data.mean()  # Recall count_data is the\n",