mathlib3

ce4a8b89 - feat(topology/algebra/group): quotient of a second countable group (#16738)

feat(topology/algebra/group): quotient of a second countable group (#16738) Quotient of a second countable group is second countable Co-authored-by: Heather Macbeth <25316162+hrmacbeth@users.noreply.github.com> Co-authored-by: Heather Macbeth <25316162+hrmacbeth@users.noreply.github.com>