fix(gatsby-plugin-mdx): Img w/ lessBabel option in src/pages not working

[LekoArts]

Description

While working on my own site I noticed a bug:

• Use gatsby-remark-images with gatsby-plugin-mdx
• use lessBabel: true option
• src/pages/art/index.mdx
• That MDX file uses an image in the same directory:

Some text blabla

![Alt text](./link-to-image.jpg)

When running gatsby develop the process failed on TypeError: getNode is not a function on this line:

gatsby/packages/gatsby-remark-images/src/index.js

Line 132 in 3bcb6e2

const parentNode = getNode(markdownNode.parent)

All the helper functions including getNode were undefined.

I don't understand why they are not all passed down anyways but for now I only added getNode