Relax childprocess constraint to allow up to version 3.x

Version 3.0.0 has been released:
https://github.com/enkessler/childprocess/releases/tag/v3.0.0

Author: sds

CHANGELOG.md

@@ -4,7 +4,7 @@
 
 * Fix Overcommit to display helpful error message when a hook does not inherit
   from the base class
-* Relax `childprocess` gem constraint to allow version 2.x
+* Relax `childprocess` gem constraint to allow up to version 3.x
 
 ## 0.49.1
 

overcommit.gemspec

@@ -27,6 +27,6 @@ Gem::Specification.new do |s|
 
   s.required_ruby_version = '>= 2.4'
 
-  s.add_dependency          'childprocess', '>= 0.6.3', '< 3.0'
+  s.add_dependency          'childprocess', '>= 0.6.3', '< 4'
   s.add_dependency          'iniparse', '~> 1.4'
 end