Drop Ruby 2.5 support

bsearch for endless range is only available in ruby >= 2.6

Author: tompng

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
     uses: ruby/actions/.github/workflows/ruby_versions.yml@master
     with:
       engine: cruby-truffleruby
-      min_version: 2.5
+      min_version: 2.6
       versions: '["debug"]'
 
   host:

bigdecimal.gemspec

@@ -53,7 +53,7 @@ Gem::Specification.new do |s|
     ]
   end
 
-  s.required_ruby_version = Gem::Requirement.new(">= 2.5.0")
+  s.required_ruby_version = Gem::Requirement.new(">= 2.6.0")
 
   s.metadata["changelog_uri"] = s.homepage + "/blob/master/CHANGES.md"
 end