[BRANDING] Move docs.gitea.com to forgejo.org/docs

- Replace links from docs.gitea.com with forgejo.org/docs for those
where the relevant links are available on the Forgejo documentation.
- Resolves #2892

templates/repo/migrate/gitea.tmpl

@@ -21,7 +21,7 @@
 					<div class="inline field {{if .Err_Auth}}error{{end}}">
 						<label for="auth_token">{{ctx.Locale.Tr "access_token"}}</label>
 						<input id="auth_token" name="auth_token" type="password" autocomplete="new-password" value="{{.auth_token}}" {{if not .auth_token}} data-need-clear="true" {{end}}>
-						<a target="_blank" href="https://docs.gitea.com/development/api-usage">{{svg "octicon-question"}}</a>
+						<a target="_blank" href="https://forgejo.org/docs/latest/user/api-usage/">{{svg "octicon-question"}}</a>
 					</div>
 
 					{{template "repo/migrate/options" .}}