chore: Update pairing_heap requirement from ~> 0.3 to >= 0.3, < 4.0 (#…

…119)

Updates the requirements on [pairing_heap](https://github.com/mhib/pairing_heap) to permit the latest version.
- [Release notes](https://github.com/mhib/pairing_heap/releases)
- [Commits](mhib/pairing_heap@v0.3.0...v3.0.1)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

rgl.gemspec

@@ -11,7 +11,7 @@ Gem::Specification.new do |s|
   #### Dependencies and requirements.
 
   s.add_dependency 'stream',     '~> 0.5.3'
-  s.add_dependency 'pairing_heap', '~> 0.3'
+  s.add_dependency 'pairing_heap', '>= 0.3', '< 4.0'
   s.add_dependency 'rexml', '~> 3.2', '>= 3.2.4'
 
   s.add_development_dependency 'rake', '~> 13.0'