package/redhat: correct dependency on package

When $package_name is not 'nginx' the dependency on the package resource would be incorrect.

Probably never an issue in practice since 'nginx' is the package name in the nginx.org repo.

manifests/package/redhat.pp

@@ -39,7 +39,7 @@ class nginx::package::redhat (
           gpgcheck => '1',
           priority => '1',
           gpgkey   => 'http://nginx.org/keys/nginx_signing.key',
-          before   => Package[$package_name],
+          before   => Package['nginx'],
         }
       }
       'nginx-mainline': {
@@ -50,7 +50,7 @@ class nginx::package::redhat (
           gpgcheck => '1',
           priority => '1',
           gpgkey   => 'http://nginx.org/keys/nginx_signing.key',
-          before   => Package[$package_name],
+          before   => Package['nginx'],
         }
       }
       default: {