updated icons for supernovae

M +- -- kstars/icons/hi22-action-kstars_supernovae.png
M +- -- kstars/icons/hi32-action-kstars_supernovae.png
M +- -- kstars/icons/hi48-action-kstars_supernovae.png
M +- -- kstars/icons/hi64-action-kstars_supernovae.png