Update parslet requirement from ~> 1.8.0, >= 1.8.0 to >= 1.8, < 2.1

Updates the requirements on [parslet](https://github.com/kschiess/parslet) to permit the latest version.
- [Changelog](https://github.com/kschiess/parslet/blob/master/HISTORY.txt)
- [Commits](kschiess/parslet@1.8.0...2.0.0)

---
updated-dependencies:
- dependency-name: parslet
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

nose.gemspec

@@ -20,7 +20,7 @@ Gem::Specification.new do |s|
   s.add_dependency 'logging', '~> 2.2.0', '>= 2.2.0'
   s.add_dependency 'mipper', '~> 0.1.0'
   s.add_dependency 'parallel', '~> 1.20.1', '>= 1.11.0'
-  s.add_dependency 'parslet', '~> 1.8.0', '>= 1.8.0'
+  s.add_dependency 'parslet', '>= 1.8', '< 2.1'
   s.add_dependency 'pickup', '~> 0.0.11'
   s.add_dependency 'pry', '~> 0.13.1'
   s.add_dependency 'rake', '~> 12.3.2', '>= 12.0.0'