8292671: Hotspot Style Guide should allow covariant returns

Reviewed-by: jrose, kbarrett, stuefe, kvn, dholmes

doc/hotspot-style.html

@@ -448,7 +448,6 @@ while ( test_foo(args...) ) { // No, excess spaces around control</code></pre></
 <li><p><code>[[deprecated]]</code> attribute (<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3760.html">n3760</a>) — Not relevant in HotSpot code.</p></li>
 <li><p>Avoid most operator overloading, preferring named functions. When operator overloading is used, ensure the semantics conform to the normal expected behavior of the operation.</p></li>
 <li><p>Avoid most implicit conversion constructors and (implicit or explicit) conversion operators. (Note that conversion to <code>bool</code> isn't needed in HotSpot code because of the &quot;no implicit boolean&quot; guideline.)</p></li>
-<li><p>Avoid covariant return types.</p></li>
 <li><p>Avoid <code>goto</code> statements.</p></li>
 </ul>
 <h3 id="undecided-features">Undecided Features</h3>

doc/hotspot-style.md

@@ -1120,8 +1120,6 @@ normal expected behavior of the operation.
 conversion operators.  (Note that conversion to `bool` isn't needed
 in HotSpot code because of the "no implicit boolean" guideline.)
 
-* Avoid covariant return types.
-
 * Avoid `goto` statements.
 
 ### Undecided Features