Doc: Issue 4323: Ensure all contexts in satb.ly template stay alive

Doc: Issue 4323: Ensure all contexts in satb.ly template stay alive

  Following the fix to Issue 2010, some contexts in deeply nested
  parallel constructs may be terminated prematurely, at least this
  is the likely explanation for the failure of the satb.ly template
  in Release 2.19.16, although blaming Issue 2010 is conjecture.

  As an alternative fix to Issue 2010 seems far away, this is a hackish
  workaround enable the satb.ly template to work in releases after
  2.19.15 by ensuring all contexts remain alive for the duration of the
  longest of them.  It corrects all the examples in the LM.