[rfc][icedtea-web] Remove 'serious' from 'A serious exception has occurred'

[Severin Gehwolf]

On Wed, 2013-05-29 at 10:33 -0400, Adam Domurad wrote:
> Changelog in patch. Motivation being people seem to not be sure what 
> serious means here. Worth dropping.

+1

Cheers,
Severin