Fix visceroid health radius and name

Visceroids are vehicle-sized (in-game at least), so their health radius should reflect that.

And yes, I'm pretty sure it should be Visceroid and not Viceroid. The majority of Westwood documents and Tiberian Suns' rules.ini clearly spell it with an 's' added before the 'c'.
Merge pull request #4373 from reaperrr/patch-1

Fix visceroid health radius and name