Move conditional inclusion from gemspec.

Conditional inclusion of libraries varies by ruby version.

Client applications that need the standard gems will need to include them on
their own.

Author: TreyE

Gemfile

@@ -4,3 +4,10 @@ source "https://rubygems.org"
 
 # Specify your gem's dependencies in resource_registry.gemspec
 gemspec
+
+if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new('3.1.0')
+    gem 'bigdecimal'
+    gem 'mutex_m'
+    gem 'base64'
+    gem 'ostruct'
+end

resource_registry.gemspec

@@ -43,13 +43,6 @@ Gem::Specification.new do |spec|
   spec.add_dependency 'ox',                       '~> 2.0'
   spec.add_dependency 'bootsnap',                 '~> 1.0'
   spec.add_dependency 'mime-types'
-  if ResourceRegistry.stdgem_ruby_version?
-    spec.add_dependency 'bigdecimal'
-    spec.add_dependency 'mutex_m'
-    spec.add_dependency 'base64'
-    spec.add_dependency 'ostruct'
-  end
-
 
   spec.add_development_dependency 'bundler',          '~> 2.0'
   spec.add_development_dependency 'rake',             '~> 12.0'