src: make approved warnings message consistent
src: make approved warnings message consistent

Currently, the warning message for approved/not approved licenses does
not line up with any unknown licenses found making the output look
sloppy.

This commit makes the headers consistent.

lgriffin/license-reporter,helio-frota/license-reporter,bucharest-gold/license-reporter,bucharest-gold/license-reporter,lgriffin/license-reporter,helio-frota/license-reporter