Update parameter_tuning_nested.py

inserted missing word

python_scripts/parameter_tuning_nested.py

@@ -215,7 +215,7 @@
 # ```
 #
 # However, this evaluation only provides us a single point estimate of the
-# generalization performance. As recall at the beginning of this notebook, it is
+# generalization performance. As you recall at the beginning of this notebook, it is
 # beneficial to have a rough idea of the uncertainty of our estimated
 # generalization performance. Therefore, we should instead use an additional
 # cross-validation for this evaluation.