Fix typo on chapter 2: catagory -> category

Author: pablooliveira

Chapter2_MorePyMC/MorePyMC.ipynb

@@ -188,7 +188,7 @@
      "source": [
       "PyMC is concerned with two types of programming variables: `stochastic` and `deterministic`.\n",
       "\n",
-      "*  *stochastic variables* are variables that are not deterministic, i.e., even if you knew all the values of the variables' parents (if it even has any parents), it would still be random. Included in this catagory are instances of classes `Poisson`, `DiscreteUniform`, and `Exponential`.\n",
+      "*  *stochastic variables* are variables that are not deterministic, i.e., even if you knew all the values of the variables' parents (if it even has any parents), it would still be random. Included in this category are instances of classes `Poisson`, `DiscreteUniform`, and `Exponential`.\n",
       "\n",
       "*  *deterministic variables* are variables that are not random if the variables' parents were known. This might be confusing at first: a quick mental check is *if I knew all of variable `foo`'s parent variables, I could determine what `foo`'s value is.* \n",
       "\n",