chore: update eslint to fix linting issues (gatsbyjs#29988)

* chore: update eslint to fix linting issues

* cleanup

* remove /

* Update packages/gatsby/src/commands/serve.ts

Co-authored-by: Matt Kane <matt@gatsbyjs.com>

* update config

* update circle to keep babel-preset-gatsby-package so we can use it in
our babel config

* fix unit tests

* fix snapshot

* fix thigns

* update gatsby-node

Co-authored-by: Matt Kane <matt@gatsbyjs.com>

src/gatsby-node.js

@@ -45,7 +45,7 @@ const createFSMachine = (
   // After 'ready', we handle the 'add' event without putting it into a queue.
   let pathQueue = []
   const flushPathQueue = () => {
-    let queue = pathQueue.slice()
+    const queue = pathQueue.slice()
     pathQueue = null
     return Promise.all(
       // eslint-disable-next-line consistent-return