fix broken diag in appendix cheat sheet

Author: hjwp

appendix_IX_cheat_sheet.asciidoc

@@ -50,8 +50,8 @@ The Basic TDD Workflow
 
 
 [[Double-Loop-TDD-diagram2]]
-.The TDD process with functional and unit tests
-image::images/twp2_0404.png["A flowchart showing functional tests as the overall cycle, and unit tests helping to code"]
+.Double-loop TDD
+image::images/double-loop-tdd-simpler.png["An inner red/green/refactor loop surrounded by an outer red/green of FTs"]
 
 
 Relevant chapters: <<chapter_04_philosophy_and_refactoring>>, <<chapter_05_post_and_database>>, <<chapter_07_working_incrementally>>