Tools: fix setup on docker

[khancyr]

Summary

pygame need freetype that are only installed with graphical things.
Pygame is used on mavproxy for joystick, so not essential

Classification & Testing (check all that apply and add your own)

• Checked by a human programmer
• Non-functional change
• No-binary change
• Infrastructure change (e.g. unit tests, helper scripts)
• Automated test(s) verify changes (e.g. unit test, autotest)
• Tested manually, description below (e.g. SITL)
• Tested on hardware
• Logs attached
• Logs available on request

[peterbarker]

LGTM