Simplify 4.1.1.6

Fixes n3554/n3554#63

Author: jaredhoberock

algorithms.html

@@ -133,10 +133,7 @@ <h1>Effect of execution policies on algorithm execution</h1>
 
       <p>
         Algorithms invoked with an execution policy object of type <code>execution_policy</code>
-        execute internally as if invoked with instances of type
-        <code>sequential_execution_policy</code>, <code>parallel_execution_policy</code>, or an
-        implementation-defined execution policy type depending on the dynamic value of the
-        <code>execution_policy</code> object.
+        execute internally as if invoked with the contained execution policy object.
       </p>
 
       <p>