fixed links on community.md
fixed links on community.md


Former-commit-id: 64a5152fe603193faf4266104ff712c37b6dbb2a [formerly 1a88dc921a594fee7b5b8cee3c279197c1b15dc4]
Former-commit-id: 792bee32305aa99a4733675a072ba5162d8f8f21
LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io