Update _07_layout.scss
Update _07_layout.scss

Former-commit-id: c6b75e3c940b1a9719bf179b13a88c03387eeb47 [formerly 060d99963f85a807f7f68f3cb55bc6c93e6dc207]
Former-commit-id: 0020e10c2a7294cd390267cb2426d43a73b2f318
LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io