Update about.md
Update about.md

remove columns

Former-commit-id: 9e57bf828a99bc1df1252904dfeb5b8cf117f48e [formerly 703a75c9e0ae1667fb398cb49cce1deeaa86f240]
Former-commit-id: 6a972a1ec0fbd294b82daed086d647ffa3290c44
LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io