[css-overflow] test coverage

Author: frivoal

css-overflow-4/Overview.bs

@@ -977,6 +977,7 @@ Indicating Block-Axis Overflow: the 'block-ellipsis' property</h3>
 			block-ellipsis-016.html
 			block-ellipsis-018.html
 			block-ellipsis-025.html
+			block-ellipsis-039.html
 			block-ellipsis-quirk-001.html
 		</wpt>