Delete UG layouts/sitemap.xml

[chalin]

• Fixes Sitemap malformed in www.docsy.dev #1897
• Drops the UG's custom layouts/sitemap.xml, which has been around since the project's inception. I'm not sure why it exists.

@LisaFC et al.: this is the diff between the UG's custom layouts/sitemap.xml and the Hugo sitemap.xml embedded template (green is the new code):

@@ -1,22 +1,24 @@
-{{ printf "<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"yes\" ?>" | safeHTML }}
+{{ printf "<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"yes\"?>" | safeHTML }}
 <urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
   xmlns:xhtml="http://www.w3.org/1999/xhtml">
   {{ range .Data.Pages }}
+    {{- if .Permalink -}}
   <url>
-    <loc>https://www.docsy.dev{{ .Permalink }}</loc>{{ if not .Lastmod.IsZero }}
+    <loc>{{ .Permalink }}</loc>{{ if not .Lastmod.IsZero }}
     <lastmod>{{ safeHTML ( .Lastmod.Format "2006-01-02T15:04:05-07:00" ) }}</lastmod>{{ end }}{{ with .Sitemap.ChangeFreq }}
     <changefreq>{{ . }}</changefreq>{{ end }}{{ if ge .Sitemap.Priority 0.0 }}
     <priority>{{ .Sitemap.Priority }}</priority>{{ end }}{{ if .IsTranslated }}{{ range .Translations }}
     <xhtml:link
                 rel="alternate"
-                hreflang="{{ .Lang }}"
+                hreflang="{{ .Language.LanguageCode }}"
                 href="{{ .Permalink }}"
                 />{{ end }}
     <xhtml:link
                 rel="alternate"
-                hreflang="{{ .Lang }}"
+                hreflang="{{ .Language.LanguageCode }}"
                 href="{{ .Permalink }}"
                 />{{ end }}
   </url>
+    {{- end -}}
   {{ end }}
-</urlset>
+</urlset>
\ No newline at end of file

I see no reason for the UG to have a custom sitemap layout, so this PR drops it.

(Thankfully, this isn't a Docsy bug!)

/cc @jmichelgarcia

[fekete-robert]

LGTM