Remove leftover comments from removed code in System.Linq.Parallel (d…

…otnet/corefx#32814)

The code was removed in dotnet/corefx#19143

Commit migrated from dotnet/corefx@de264c5

src/libraries/System.Linq.Parallel/src/System/Linq/Parallel/QueryOperators/Unary/SortQueryOperator.cs

@@ -76,14 +76,6 @@ IOrderedEnumerable<TInputOutput> IOrderedEnumerable<TInputOutput>.CreateOrderedE
             return new SortQueryOperator<TInputOutput, Pair<TSortKey, TKey2>>(Child, pairKeySelector, pairComparer, false);
         }
 
-        //---------------------------------------------------------------------------------------
-        // Accessor the key selector.
-        //
-
-        //---------------------------------------------------------------------------------------
-        // Accessor the key comparer.
-        //
-
         //---------------------------------------------------------------------------------------
         // Opens the current operator. This involves opening the child operator tree, enumerating
         // the results, sorting them, and then returning an enumerator that walks the result.
@@ -199,9 +191,6 @@ internal SortQueryOperatorEnumerator(QueryOperatorEnumerator<TInputOutput, TKey>
             _source = source;
             _keySelector = keySelector;
         }
-        //---------------------------------------------------------------------------------------
-        // Accessor for the key comparison routine.
-        //
 
         //---------------------------------------------------------------------------------------
         // Moves to the next element in the sorted output. When called for the first time, the