fix typo in comment [ci skip].

Author: senny

activesupport/lib/active_support/test_case.rb

@@ -22,7 +22,7 @@ class << self
 
   def self.__run reporter, options # :nodoc:
     # FIXME: MT5's runnables is not ordered. This is needed because
-    # we have have tests have cross-class order-dependent bugs.
+    # we have tests with cross-class order-dependent bugs.
     suites = Runnable.runnables.sort_by { |ts| ts.name.to_s }
 
     parallel, serial = suites.partition { |s| s.test_order == :parallel }