fix: Use correct Ruby for Nginx (#5607)

**Story card:**
[sc-15637](https://app.shortcut.com/simpledotorg/story/15637)

## Because

Nginx pointing to a now non-existent Ruby — because of the Ruby upgrades
going on — causes SBX to 503

## This addresses

Using the right Ruby version in Nginx

## Test instructions

a healthy SBX

Author: igbanam

.docker/config/nginx/webapp.conf

@@ -8,7 +8,7 @@ server {
   gzip_types text/html text/plain application/json;
 
   passenger_user app;
-  passenger_ruby /usr/bin/ruby2.7;
+  passenger_ruby /usr/local/bin/ruby;
   passenger_app_root /home/app;
   passenger_enabled on;
   passenger_app_env production;

.semaphore/semaphore.yml

@@ -27,7 +27,7 @@ blocks:
             - cache store
   - name: Tests
     skip:
-      when: change_in(['/doc', '/swagger', '**/*.md', '/public', '/script'])
+      when: change_in([ '**/*.md', '/.*', '/doc', '/public', '/script', '/swagger' ])
     task:
       env_vars:
         - name: RAILS_ENV