Fix comment to make it less ambiguous

Author: aycabta

test/test_rake_functional.rb

@@ -309,7 +309,7 @@ def test_update_midway_through_chaining_to_file_task
     rake "-n"
     assert_equal(%w{fileA fileB fileC default}, dryrun_tasks)
     rake
-    sleep 1 # for stride seconds surely for timestamp
+    sleep 1 # Ensure the timestamp is on a new second
     FileUtils.touch("fileA")
     rake "-n"
     assert_equal(%w{fileB fileC default}, dryrun_tasks)