[Snyk] Upgrade gatsby-plugin-mdx from 2.6.0 to 2.15.0#375

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

snyk-upgrade-4c6c1bf86792e6264d5c3b1b593ad0a8ibm-self-serve-assets/ibm-gsi-cloudnative-journey:snyk-upgrade-4c6c1bf86792e6264d5c3b1b593ad0a8Copy head branch name to clipboard