[DOC] Update comment of assert_pattern_list

`pattern_list` may contain string since d903e76726.

tool/lib/core_assertions.rb

@@ -541,11 +541,11 @@ eom
         refute_respond_to(obj, meth, msg)
       end
 
-      # pattern_list is an array which contains regexp and :*.
+      # pattern_list is an array which contains regexp, string and :*.
       # :* means any sequence.
       #
       # pattern_list is anchored.
-      # Use [:*, regexp, :*] for non-anchored match.
+      # Use [:*, regexp/string, :*] for non-anchored match.
       def assert_pattern_list(pattern_list, actual, message=nil)
         rest = actual
         anchored = true