refactor: remove out-of-scope pageQuery fix

Author: axe312ger

packages/gatsby-plugin-mdx/src/gatsby-layout-loader.ts

@@ -68,11 +68,6 @@ const gatsbyLayoutLoader: LoaderDefinition = async function () {
     type: `mdxjsEsm` as `text`,
     value: `import GatsbyMDXLayout from "${layoutPath}"`,
   })
-  tree.children.push({
-    type: `mdxjsEsm` as `text`,
-    value: `export * from "${layoutPath}"`,
-  })
-
   tree.children.push({
     type: `mdxjsEsm` as `text`,
     value: `export default GatsbyMDXLayout`,