Changed the secondary title on hierarchy index to "Class hierarchy".

This is more or less cosmetic, but it fits nicer to the class reference index descriptions and avoids repetition with the main title.

XHTMLGenerator.m

@@ -618,9 +618,7 @@ - (void) appendHierarchyHeaderToData:(NSMutableData*) data
 	[self appendLine:@"    <div class=\"hierarchy\">" toData:data];
 
 	// Append the title.
-	[self appendString:@"      <h5>" toData:data];
-	[self appendString:self.hierarchyTitle toData:data];
-	[self appendLine:@"</h5>" toData:data];
+	[self appendLine:@"      <h5>Class hierarchy</h5>" toData:data];
 
 	// Prepare the default group indent. We use this so that the XHTML code is visually
 	// more readable, however it doesn't add to the actual appearance...