gatsby-theme-i18n adds trailing slash even if trailingSlash is set to never

[gugu]

Expected behaviour for location / and trailingSlash=never:

<link data-react-helmet="true" rel="alternate" hrefLang="x-default" href="https://short.io/"/>
<link data-react-helmet="true" rel="alternate" hrefLang="ru" href="https://short.io/zh"/> <!-- current -->
<link data-react-helmet="true" rel="alternate" hrefLang="en-US" href="https://short.io/"/>
<link data-react-helmet="true" rel="alternate" hrefLang="ja" href="https://short.io/ja"/>
<link data-react-helmet="true" rel="alternate" hrefLang="de" href="https://short.io/de"/>

current behaviour:

<link data-react-helmet="true" rel="alternate" hrefLang="x-default" href="https://short.io/"/>
<link data-react-helmet="true" rel="alternate" hrefLang="ru" href="https://short.io/zh"/> <!-- current -->
<link data-react-helmet="true" rel="alternate" hrefLang="en-US" href="https://short.io/"/>
<link data-react-helmet="true" rel="alternate" hrefLang="ja" href="https://short.io/ja/"/> <!-- extra slash -->
<link data-react-helmet="true" rel="alternate" hrefLang="de" href="https://short.io/de/"/> <!-- extra slash -->
...