Add note explaining instrumenters are no longer needed (#301)
Add note explaining instrumenters are no longer needed (#301)

* Add note explaining instrumenters are no longer needed

* Update source/elixir/integrations/phoenix.html.md

Co-Authored-By: Tom de Bruijn <96835dd8bfa718bd6447ccc87af89ae1675daeca@tomdebruijn.com>

* Mention Phoenix 1.4.7 and up for instrumenters

Co-authored-by: Tom de Bruijn <96835dd8bfa718bd6447ccc87af89ae1675daeca@tomdebruijn.com>

appsignal/appsignal-docs