[ruby/irb] Silent the noise created when building Context in tests

https://github.com/ruby/irb/commit/27e4274b3c

test/irb/test_ruby_lex.rb

@@ -721,6 +721,7 @@ module TestIRB
         end
       end
 
+      IRB.conf[:VERBOSE] = false
       IRB::Context.new(nil, workspace)
     end
   end