add Style/Lambda to .rubocop.yml

git-svn-id: http://svn.redmine.org/redmine/trunk@20658 e93f8b46-1217-0410-a6f0-8f06a7374b81

Author: marutosi

.rubocop.yml

@@ -185,6 +185,10 @@ Style/IdenticalConditionalBranches:
     - 'config/initializers/10-patches.rb'
     - 'lib/redmine/wiki_formatting/textile/redcloth3.rb'
 
+Style/Lambda:
+  Enabled: true
+  EnforcedStyle: lambda
+
 Style/NegatedIfElseCondition:
   Enabled: false