fix unintended strikethrough in commandLine forkedMode documentation

In the section heading for "Debugging and Forked Execution (--debug vs --debug-fork)",
the double-hyphens before the --debug and --debug-fork were not being rendered correctly,
and debug was being rendered as a strikethrough.  This change appears to result in the
intended rendering.
Merge pull request #173 from davidmc24/fix-debug-strikethrough

fix unintended strikethrough in commandLine forkedMode documentation