match-parameters: fix sub-directory names of stbt-debug directory

Since stbt-0.14 and particularly
https://github.com/drothlis/stb-tester/commit/4e7de9dc6491a31b760f9b92e840b80bd1da2581
the subdirectories of stbt-debug have changed. The article has been altered
to reflect the changes.
match-parameters: Remove incorrect stbt-debug documentation

Since 4e7de9dc, the debug images for each frame are saved in a different
numbered directory (stbt-debug/detect_match/00001 etc).