Update unicode-display_width requirement from >= 1.7, < 3.0 to >= 1.7…

…, < 4.0

Updates the requirements on [unicode-display_width](https://github.com/janlelis/unicode-display_width) to permit the latest version.
- [Changelog](https://github.com/janlelis/unicode-display_width/blob/main/CHANGELOG.md)
- [Commits](janlelis/unicode-display_width@v1.7.0...v2.6.0)

---
updated-dependencies:
- dependency-name: unicode-display_width
  dependency-type: direct:production
...

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

colorls.gemspec

@@ -65,7 +65,7 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency 'filesize', '~> 0'
   spec.add_runtime_dependency 'manpages', '~> 0'
   spec.add_runtime_dependency 'rainbow', '>= 2.2', '< 4.0'
-  spec.add_runtime_dependency 'unicode-display_width', '>= 1.7', '< 3.0'
+  spec.add_runtime_dependency 'unicode-display_width', '>= 1.7', '< 4.0'
 
   spec.add_development_dependency 'bundler', '~> 2.0'
   spec.add_development_dependency 'codecov', '~> 0.1'