Remove .txt file extension from create_fake_doc()

@@ -20,7 +20,7 @@ def description_with_id(prefix, sentence):
 
 def create_fake_doc():
     content = fake.text()
-    suffix = fake.random_element(('.txt', '.doc', '.docx', '.pdf'))
+    suffix = fake.random_element(('.doc', '.docx', '.pdf'))
     tf = NamedTemporaryFile(delete=False, suffix=suffix)
     tf.write(content)
     tf.close()