Fix issue with random number tool in smol_tools

[lionelchg]

Currently since the get_random_number_between function in agent.py returns an integer, when prompting the agent to output a random number the following error is thrown:

python demo_tkinter.py
[...] # Press F10
======== New task ========
random 1-10
error PIL must be installed in order to handle images.

The PR convers to string the random integer and fixes the above error