fix typo in quickstart guide

docs/quickstart.rst

@@ -513,7 +513,7 @@ attributes mentioned above::
                 return log_the_user_in(request.form['username'])
             else:
                 error = 'Invalid username/password'
-        # the code below this is executed if the request method
+        # the code below is executed if the request method
         # was GET or the credentials were invalid
         return render_template('login.html', error=error)