fix: graphql version error in production (#14622)

A graphql version error may be thrown in production, as we're no longer
externalizing the graphql dependency. This PR fixes this by adding back
graphql to `serverExternalPackages`.


[PAYL-397](https://linear.app/figma-trial/issue/PAYL-397/graphql-version-issue-in-364-due-to-serverexternalpackages)

Author: AlessioGr

packages/next/src/withPayload.js

@@ -128,6 +128,10 @@ export const withPayload = (nextConfig = {}, options = {}) => {
       '@payloadcms/payload-cloud',
       // External, because it installs import-in-the-middle and require-in-the-middle - both in the default serverExternalPackages list.
       '@sentry/nextjs',
+      // Can be externalized, because we require users to install graphql themselves - we only rely on it as a peer dependency.
+      // WHY: without externalizing graphql, a graphql version error will be thrown
+      // during runtime ("Ensure that there is only one instance of \"graphql\" in the node_modules\ndirectory.")
+      'graphql',
       // TODO: We need to externalize @payloadcms/storage-s3 as well, once Next.js has the ability to exclude @payloadcms/storage-s3/client from being externalized.
       // Do not bundle additional server-only packages during dev to improve compilation speed
       ...(process.env.NODE_ENV === 'development' && options.devBundleServerPackages === false