[fix] typo

Author: ngjunsiang

Programming in Python/lesson_08.ipynb

@@ -47,7 +47,7 @@
     "    for word in text.split(\" \"):\n",
     "        record[\"word\"] = word\n",
     "        for char in word:\n",
-    "            if char in \"aeiou\":\n",
+    "            if char.lower() in \"aeiou\":\n",
     "                record[\"vowels\"] = record[\"vowels\"] + 1\n",
     "            record[\"length\"] = record[\"length\"] + 1\n",
     "        records.append(record)\n",