Just change export syntax

src/components/Head.js

@@ -2,7 +2,7 @@ import React from 'react'
 import Helmet from 'react-helmet'
 import useSiteMetadata from './use-site-metadata'
 
-function Head(props) {
+export default function Head(props) {
   const siteMetadata = useSiteMetadata()
   const title = props.title ? `${props.title} | ${siteMetadata.title}` : siteMetadata.title
   const description = props.description || siteMetadata.description
@@ -19,6 +19,4 @@ function Head(props) {
       <script src="https://analytics.githubassets.com/hydro-marketing.min.js"></script>
     </Helmet>
   )
-}
-
-export default Head
+}