[doc] Minor fix

Summary:
Don't interrupt user's flow that they may need to install `tabulate`.
Also, show them the actual command that they need to run to install
`tabulate`.

Add this to the prereqisite section.

Test Plan:
Look at rendered doc.

Author: c-p-i-o

prototype_source/flight_recorder_tutorial.rst

@@ -11,6 +11,13 @@ Prerequisites
 -------------
 - PyTorch version 2.5 or later.
 
+Install the `tabulate` python module.
+
+.. code:: shell
+
+  pip install tabulate
+
+
 Overview
 --------
 An AI distributed training job refers to the process of training a machine learning model using multiple devices, such
@@ -199,6 +206,9 @@ Caveat: tabulate module is needed, so you might need pip install it first.
   python fr_trace.py <dump dir containing trace files> -j [--selected-ranks i j k ...] [--pg-filters tp dp]
   torchfrtrace <dump dir containing trace files> -j [--selected-ranks i j k ...] [--pg-filters 0 2]
 
+
+
+
 Conclusion
 ----------
 In this tutorial, we have learned about a new PyTorch diagnostic tool called Flight Recorder.