[Snyk] Upgrade gatsby-plugin-mdx from 2.6.0 to 2.15.0#373

mjperrins wants to merge 1 commit intodev-advancedibm-self-serve-assets/ibm-gsi-cloudnative-journey:dev-advancedfrom

snyk-upgrade-96c446fb6febbee1c5aa5a569a20c4acibm-self-serve-assets/ibm-gsi-cloudnative-journey:snyk-upgrade-96c446fb6febbee1c5aa5a569a20c4acCopy head branch name to clipboard