Fixed the margins on the class diagram dropdown image after all images were globally given a margin if 20px (I wish this could have been done differently, but it doesn't look like there's any better way of making sure the right images in the manual have a reasonable margin).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58435 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/doxygen/wxwidgets.css

@@ -413,6 +413,10 @@ IMG.appearance {
 	margin: 20px;
 }
 
+.dynheader IMG {
+    margin: 0px;
+}
+
 TABLE.appearance {
 	width: 100%;
 	text-align: center;