Fixed pseudo-typo in Spanish options.rpy

- Before 1999, the adverb 'solo' took the tilde in all cases.
- After 1999, it was optional. (Diccionario Panhispánico de dudas)
- With the new grammar (2009-2011) this tilde is not allowed.

references:
http://reglasespanol.about.com/b/2012/08/28/nueva-ortografia-solo-sin-acento.htm
http://blog.lengua-e.com/2007/solo-con-tilde-o-sin-tilde/