move font import statement to within the use-theme conditional

This is so that any repo using bagel can exclude this call if using its own chrome style.
An app that requires all resource to be local and no calls to non https link will definitely need this.
e.g.
iconset:
  include: true
  theme:
    prototype: false
    mytheme: true

still caused problem because this @import to google font is outside of the use-theme conditional. it was being compiled in regardless of an app's own config.yml setting.