Duplicate "gatsby-transformer-asciidoc" in "gatsby-config.js" #532

Reproduction steps

• Open file gatsby-config.js
• Observe -- once it exists as a string and once as an object, which causes the plugin to be loaded twice.

Expected Results

• That object of "gatsby-transformer-asciidoc" should be there just

Actual Results

It exists two times

Anything else?

I have checked that the project will work fine by removing.
build was ok
project was running