fix(nginx): add redirect for /api/v2/ trailing slash

When accessing /api/v2/ with a trailing slash, the page returned a 404 error.
This adds a redirect to remove the trailing slash, matching the behavior of
other similar paths like /sdk/js/, /cli/, etc.

Slack thread: https://apify.slack.com/archives/C0L33UM7Z/p1770281199186039

https://claude.ai/code/session_01GqcrG6JU9Y1YaSA5ns87Yz

Author: claude

nginx.conf

@@ -460,6 +460,9 @@ server {
     rewrite ^/sdk/python/$ /sdk/python redirect;
     rewrite ^/cli/$ /cli redirect;
 
+    # remove trailing slash from api reference index
+    rewrite ^/api/v2/$ /api/v2 redirect;
+
     # versions page redirects
     rewrite ^/versions/?$ / permanent; # no docs-wide changelog, redirect to the root
     rewrite ^/cli/versions/?$ /cli/docs/changelog permanent;