Fix typo

one -> once

Author: j-min

DP/Policy Evaluation.ipynb

@@ -42,7 +42,7 @@
     "        policy: [S, A] shaped matrix representing the policy.\n",
     "        env: OpenAI env. env.P represents the transition probabilities of the environment.\n",
     "            env.P[s][a] is a (prob, next_state, reward, done) tuple.\n",
-    "        theta: We stop evaluation one our value function change is less than theta for all states.\n",
+    "        theta: We stop evaluation once our value function change is less than theta for all states.\n",
     "        discount_factor: lambda discount factor.\n",
     "    \n",
     "    Returns:\n",