remove broken str lt/gt regress test for now
remove broken str lt/gt regress test for now

lib/modernish/tst/string.t:
- Regress-testing 'str lt' and 'str gt' is difficult because it may
  use different commands, which don't always quite agree with each
  other or with 'sort' about what sorts before what -- and it's
  also locale-dependent. Replacing it with a trivial test that
  checks the functionality is at least there.

modernish/modernish