Fix equality assertion causing test error

eql is primarily used as a mathematical equals. Using it here was
causing a divison by 0 error due to some confusion.

Co-authored-by: Seth Boyles <sboyles@pivotal.io>
Co-authored-by: Mona Mohebbi <mmohebbi@pivotal.io>

spec/unit/lib/sinatra/vcap_spec.rb

@@ -58,7 +58,7 @@ def app
 
   shared_examples 'http header content type' do
     it 'should return json content type in the header' do
-      expect(last_response.headers['Content-Type']).to eql('application/json;charset=utf-8')
+      expect(last_response.headers['Content-Type']).to eq('application/json;charset=utf-8')
     end
   end