[bug] beta string too long

[Duke-M-commits]

That one should be made much shorter.

• The categories name is already "Betas", the rest of the screen is overflown with the word beta too.
• The tip about not being able to play with non-beta versions is already on the main menu screen.

Suggestions:

1. None
2. Next - the upcoming version
3. Bugtest - specific feature testing

or

1. None
2. Upcoming (frequent updates)
3. Bugtest (%1)

or

1. Marine (no beta) I guess this one's not possible since it's already translated by the steam client
2. Pioneer (frequent upcoming features and bugs)
3. Hunter (specific bug testing)

PS: please make these translateable too :)