tweak docstring rspec#126 [ci skip]

spec/rspec/matchers/dsl_spec.rb

@@ -5,7 +5,7 @@ def question?
     :answer
   end
 
-  it "able to use custom matchers inside custom matcher" do
+  it "supports calling custom matchers from within other custom matchers" do
     RSpec::Matchers.define :be_ok do
       match { |actual| actual.should == "ok" }
     end