.rubocop.yml in buildkit-1.5.0 vs .rubocop.yml in buildkit-1.6.0

- old
+ new

@@ -1,9 +1,6 @@
 inherit_from: .rubocop_todo.yml
 
-AllCops:
-  TargetRubyVersion: 2.3
-
 Metrics/LineLength:
   Max: 120
 
 Metrics/MethodLength:
   Max: 25