FIX: update ruby verions (2.7.1 instead off 2.6.5)

Refs: #19

manifests/default.pp

@@ -146,7 +146,7 @@ class { 'rbenv':
   owner       => $_system_username,
 }
 rbenv::plugin { 'rbenv/ruby-build': }
--> rbenv::build { '2.6.5': global => true }
+-> rbenv::build { '2.7.1': global => true }
 
 # Ensure permissions on /usr/bin/env
 -> file { '/usr/bin/env':