.rubocop.yml in x25519-1.0.8 vs .rubocop.yml in x25519-1.0.9

- old
+ new

@@ -1,6 +1,6 @@
 AllCops:
-  TargetRubyVersion: 2.2
+  TargetRubyVersion: 2.5
   DisplayCopNames: true
 
 #
 # Metrics
 #