py-pyparsing: updated to 3.0.8

Version 3.0.8
-------------
- API CHANGE: modified pyproject.toml to require Python version
  3.6.8 or later for pyparsing 3.x. Earlier minor versions of 3.6
  fail in evaluating the `version_info` class (implemented using
  `typing.NamedTuple`). If you are using an earlier version of Python
  3.6, you will need to use pyparsing 2.4.7.

- Improved pyparsing import time by deferring regex pattern compiles.

- Updated build to use flit, PR by Michaﾅ� Gﾃｳrny, added BUILDING.md
  doc and removed old Windows build scripts - nice cleanup work!

- More type-hinting added for all arithmetic and logical operator
  methods in `ParserElement`. PR from Kazantcev Andrey, thank you.

- Fixed `infix_notation`'s definitions of `lpar` and `rpar`, to accept
  parse expressions such that they do not get suppressed in the parsed
  results. PR submitted by Philippe Prados, nice work.

- Fixed bug in railroad diagramming with expressions containing `Combine`
  elements. Reported by Jeremy White, thanks!

- Added `show_groups` argument to `create_diagram` to highlight grouped
  elements with an unlabeled bounding box.

- Added `unicode_denormalizer.py` to the examples as a demonstration
  of how Python's interpreter will accept Unicode characters in
  identifiers, but normalizes them back to ASCII so that identifiers
  `print` and `�摯｡�搏ｻ盞｢�搏��攪〜 and `�摶呆搨汝摎を搗帋ｵ輿 are all equivalent.

- Removed imports of deprecated `sre_constants` module for catching
  exceptions when compiling regular expressions. PR submitted by
  Serhiy Storchaka, thank you.


(adam)