Remove the duplicate overview tag

Author: Felicity Chapman

cpp/ql/src/Critical/OverflowCalculated.qhelp

@@ -13,7 +13,6 @@ zero terminator into consideration.</li>
 <li><code>strcat</code> or <code>strncat</code> that use buffers that are too small to contain the new string.</li>
 </ul>
 </p>
-</overview>
 
 <p>
 The highlighted expression will cause a buffer overflow because the buffer is too small to contain
@@ -22,8 +21,8 @@ if the array is on stack-allocated memory).
 </p>
 
 <include src="aliasAnalysisWarning.qhelp" />
-
 </overview>
+
 <recommendation>
 <p>
 Increase the size of the buffer being allocated.