Bump required_ruby_version to 2.0 to match README

Author: ivoanjo

CHANGELOG.md

@@ -1,3 +1,7 @@
+## [0.10.13](https://github.com/ruby-debug/debase-ruby_core_source/compare/v0.10.12...v0.10.13)
+
+* updated `required_ruby_version` to require ruby 2.0
+
 ## [0.10.10](https://github.com/ruby-debug/debase-ruby_core_source/compare/v0.10.9...v0.10.10)
 
 * removed ruby 2.7.0 preview sources to avoid falling back on them for release versions

debase-ruby_core_source.gemspec

@@ -12,7 +12,7 @@ Gem::Specification.new do |s|
   s.description = %q{Provide Ruby core source files for C extensions that need them.}
   s.license = "MIT"
   s.required_rubygems_version = ">= 1.3.6"
-  s.required_ruby_version = '>= 1.9.3'
+  s.required_ruby_version = '>= 2.0.0'
   s.extra_rdoc_files = [ "README.md"]
   s.files = `git ls-files`.split("\n")
   s.add_development_dependency "archive-tar-minitar", ">= 0.5.2"