Don't emit the diff if samples db is out of date

There's a warning message emitted with instructions, a 2000 line diff
does nothing to help the user track down the issue.

test/test_samples.rb

@@ -23,8 +23,6 @@ class TestSamples < Test::Unit::TestCase
       actual.write Yajl::Encoder.encode(latest, :pretty => true)
       actual.close
 
-      warn `diff #{expected.path} #{actual.path}`
-
       expected.unlink
       actual.unlink
     end