Bump Elixir 1.13.x to 1.13.3 on CI
Bump Elixir 1.13.x to 1.13.3 on CI

1.13.3 was released on Febuary 9th.

appsignal/appsignal-elixir,appsignal/appsignal-elixir,appsignal/appsignal-elixir,appsignal/appsignal-elixir