update footer link to new landing page (#26916)

as title

Co-authored-by: Giteabot <teabot@gitea.io>

templates/base/footer_content.tmpl

@@ -1,6 +1,6 @@
 <footer class="page-footer" role="group" aria-label="{{.locale.Tr "aria.footer"}}">
 	<div class="left-links" role="contentinfo" aria-label="{{.locale.Tr "aria.footer.software"}}">
-		<a target="_blank" rel="noopener noreferrer" href="https://gitea.io">{{.locale.Tr "powered_by" "Gitea"}}</a>
+		<a target="_blank" rel="noopener noreferrer" href="https://about.gitea.com">{{.locale.Tr "powered_by" "Gitea"}}</a>
 		{{if (or .ShowFooterVersion .PageIsAdmin)}}
 			{{.locale.Tr "version"}}:
 			{{if .IsAdmin}}