Remove legacy guards for non rbx environment in specs

spec/integration/loader_spec.rb

@@ -1,13 +1,12 @@
 require 'spec_helper'
 
-if "".respond_to?(:to_ast)
-  class CodeLoadingSubject
+class CodeLoadingSubject
   def x
     true
   end
-  end
+end
 
-  describe Mutant, 'code loading' do
+describe Mutant, 'code loading' do
   let(:context) { Mutant::Context::Constant.build(CodeLoadingSubject) }
   let(:node)    { 'def foo; :bar; end'.to_ast                         }
   let(:root)    { context.root(node)                                  }
@@ -19,5 +18,4 @@ if "".respond_to?(:to_ast)
   it 'should add the method to subject' do
     CodeLoadingSubject.new.foo.should be(:bar)
   end
-  end
 end

spec/integration/method_matching_spec.rb

@@ -1,7 +1,6 @@
 require 'spec_helper'
 
-if "".respond_to?(:to_ast)
-  describe Mutant, 'method matching' do
+describe Mutant, 'method matching' do
   after do
     if defined?(::Foo)
       Object.send(:remove_const, 'Foo')
@@ -250,5 +249,4 @@ if "".respond_to?(:to_ast)
       end
     end
   end
-  end
 end

spec/unit/mutant/context/constant/root_spec.rb

@@ -1,7 +1,6 @@
 require 'spec_helper'
 
-if "".respond_to?(:to_ast)
-  describe Mutant::Context::Constant, '#root' do
+describe Mutant::Context::Constant, '#root' do
   subject { object.root(node) }
 
   let(:object) { described_class.build(SampleSubjects::ExampleModule) }
@@ -20,5 +19,4 @@ if "".respond_to?(:to_ast)
   it 'should place the ast under scope' do
     scope_body.should be(node)
   end
-  end
 end