Bump gatsby from 2.21.19 to 2.21.21

[dependabot-preview]

Bumps gatsby from 2.21.19 to 2.21.21.

Commits

• a59c441 chore(release): Publish
• 92c1be5 Errant file deletion broke prism in theme (#23911)
• 919e517 feat(benchmarks): Add script to update 1 Contentful article (for benchmarking...
• f23528d chore(starter):update gatsby-starter-typescript-power-blog template (#23071)
• 9b791aa chore(gatsby): cleanup double import of reporter (#23906)
• 4b43c99 Remove netlify.toml since we don't build on Netlify anymore
• 4fb4b3a chore(gatsby): Drop (experimental) support for Loki (#23838)
• 5a77b2f chore(release): Publish
• b130a8e fix(gatsby-dev-cli): fix set-path-to-repo command after yargs bump (#23899)
• a3815c3 chore(release): Publish
• Additional commits viewable in compare view

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