enhance: update collection install to be a one liner

Author: LaurenceJJones

crowdsec-docs/docs/appsec/quickstart/nginxopenresty.mdx

@@ -52,8 +52,7 @@ You can always view the content of a [collection on the hub](https://app.crowdse
 :::
 
 ```
-sudo cscli collections install crowdsecurity/appsec-virtual-patching
-sudo cscli collections install crowdsecurity/appsec-generic-rules
+sudo cscli collections install crowdsecurity/appsec-virtual-patching crowdsecurity/appsec-generic-rules
 ```
 
 Executing this command will install the following items: