Energy Legend suggestions

[pixelzoom]

Noted while working on phetsims/joist#413.

masses-and-springs and pendulum-lab both have a dialog titled "Energy Legend"., but their styling is different.

masses-and-springs:

pendulum-lab:

Consider making the title larger and the font of the symbols bold in masses-and-springs.

[Denz1994]

Checking for quick fix.

[arouinfar]

Thanks @pixelzoom. That is a great suggestion.

@Denz1994 a few tweaks for you

• Font sizes should match pendulum-lab
• Make energy symbols bold
• Total energy abbreviation should be E_total, not E_tot.

[Denz1994]

Can you double check the fixes in master @arouinfar?

[arouinfar]

Looks great, thanks @Denz1994!

[arouinfar]

While this was not technically for phetsims/qa#129, I'm going to go ahead and tag it so it shows up in the RC issue. That way, it'll be easier to keep track of the changes made.