update associations.md (#2352)
update associations.md (#2352)

Co-authored-by: k-maekawa <e2e19f88a45ba080489a12f3fe5b55431cd8369e@gmail.com>
doomspork/elixir_school,doomspork/elixir-school,doomspork/elixir-school,doomspork/elixir_school,nscyclone/elixir-school,doomspork/elixir-school,doomspork/elixir_school,nscyclone/elixir-school,nscyclone/elixir-school,nscyclone/elixir-school