[maintenance] Upgrade Gatsby JS ecosystem packages in Paragon

[adamstankiewicz]

Ensure Gatsby packages are upgraded to latest.

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We recently added support via @edx/frontend-build (v12.6.0) for MFEs to use @custom-media queries to support using CSS variables in media queries.

It's unclear if there is a similar change required to ensure @custom-media is supported in Paragon's Gatsby documentation website.

For example, will we need to add the postcss-custom-media plugin to gatsby-node.js and/or gatsby-config.js to add support for @custom-media?

### Acceptance Criteria
- [ ] Ensure the Paragon documentation website supports `@custom-media`.
- [ ] Upgrade Gatsby-related packages through Paragon.

[PKulkoRaccoonGang]

PR (DRAFT): https://github.com/openedx/paragon/pull/2767