Merge pull request optuna#5685 from kAIto47802/doc-add-pandas-installation-guide

Add `pandas` installation guide to RDB tutorial

Author: not522

tutorial/20_recipes/001_rdb.py

@@ -77,6 +77,12 @@ def objective(trial):
 # Experimental History
 # --------------------
 #
+# Note that this section requires the installation of `Pandas <https://pandas.pydata.org/>`__:
+#
+# .. code-block:: bash
+#
+#     $ pip install pandas
+#
 # We can access histories of studies and trials via the :class:`~optuna.study.Study` class.
 # For example, we can get all trials of ``example-study`` as: