Repair boolean

```
nginx: [emerg] invalid value "True" in "proxy_ssl_verify" directive, it
must be "on" or "off" in /etc/nginx/vhosts.d/agola.conf:14
```

Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>

pillar/cluster/denc/web-proxy.sls

@@ -221,7 +221,7 @@ nginx:
             - server_name: ci.lysergic.dev ci.git.com.de
             - location /:
               - proxy_pass: https://ci.lysergic.dev
-              - proxy_ssl_verify: true
+              - proxy_ssl_verify: on
 
 manage_firewall: True
 firewalld: