[chore] Drop long-deprecated global variable setting during embedded usage

CHANGELOG.md

@@ -22,6 +22,7 @@ Breaking Ruby API changes
 - Drop deprecated `JRuby::Rack::RailsFileSystemLayout` alias for `JRuby::Rack::FileSystemLayout`
 - Drop deprecated `JRuby::Rack::Errors` alias for `JRuby::Rack::ErrorApp`
 - Drop deprecated `Rack::Handler::Servlet::Env` and `Rack::Handler::Servlet::LazyEnv` types (replaced by `DefaultEnv`)
+- Drop deprecated setting of global `$servlet_context` variable during embedded usage (replaced by `JRuby::Rack.context`)
 
 Breaking configuration capability changes 
 - Drop `jruby.rack.jruby.version` and `jruby.rack.rack.release` keys from rack `env` Hash

src/main/java/org/jruby/rack/embed/Dispatcher.java

@@ -44,9 +44,6 @@ private void initialize() {
         IRubyObject rackModule = runtime.getModule("JRuby").getConstantAt("Rack");
         // `JRuby::Rack.context = context`
         rackModule.callMethod(runtime.getCurrentContext(), "context=", rubyContext);
-        // TODO @deprecated only doing this due backwards compatibility :
-        // user code should use JRuby::Rack.context instead of $servlet_context
-        runtime.getGlobalVariables().set("$servlet_context", rubyContext);
     }
 
     @Override
@@ -68,7 +65,6 @@ public void destroy() {
     protected void afterException(
             RackEnvironment env, Exception re,
             RackResponseEnvironment response) throws IOException {
-        // TODO a fast draft (probably should use rack.errors) :
         context.log("Error:", re);
         response.sendError(500);
     }

src/spec/ruby/rack/embed/dispatcher_spec.rb

@@ -5,13 +5,6 @@
   let(:application) { double "application" }
   let(:context) { org.jruby.rack.embed.Context.new "test" }
 
-  before { $servlet_context = nil }; after { $servlet_context = nil }
-
-  it "initializes $servlet_context", :deprecated => true do
-    org.jruby.rack.embed.Dispatcher.new context, application
-    expect($servlet_context).to be(context)
-  end
-
   it "initializes JRuby::Rack.context" do
     prev_context = JRuby::Rack.context
     JRuby::Rack.context = nil