Fix typo in gatsby-remark-code-repls sample `gatsby-config.json` in README (#10361)
Fix typo in gatsby-remark-code-repls sample `gatsby-config.json` in README (#10361)

Sample `gatsby-config.json` in `gatsby-remark-code-repls` had incorrect JSON in README due to an extra closing parenthesis.
0x80/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,ChristopherBiscardi/gatsby,0x80/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,ChristopherBiscardi/gatsby,ChristopherBiscardi/gatsby,ChristopherBiscardi/gatsby,0x80/gatsby