Update C43 to add test case for Focus Not Obscured Enhanced (#3534)

Closes #3532

---------

Co-authored-by: Patrick H. Lauke <[email protected]>

Author: fstrr

techniques/css/C43.html

@@ -167,12 +167,14 @@ <h3>Procedure</h3>
 				<p>For each user interface component that can receive keyboard focus:</p>
 				<ol>
 					<li>Check that the user interface component is not entirely hidden when it receives keyboard focus.</li>
+          <li>Check that no part of the user interface component is hidden when it receives keyboard focus.</li>
 				</ol>
 			</section>
 			<section class="test-results">
 				<h3>Expected Results</h3>
 				<ul>
 					<li>Check #1 is true.</li>
+          <li>For Focus Not Obscured (Enhanced) (Level AAA), #2 is also true.</li>
 				</ul>
 			</section>
 		</section>