Erlang modules missing from hexdocs in 1.2.1

[aaronrenner]

In opentelemetry_api 1.2.1, the erlang modules are missing from the hexdocs.

1.2.0	1.2.1

I'm guessing this wasn't intentional because those erlang APIs are very much needed.

[tsloughter]

Thanks, you're right, it was not intentional.