[css-tables-3] Allow overflow:clip to apply to table root and table wrapper boxes (w3c#7492)

Author: khushalsagar

css-tables-3/Overview.bs

@@ -926,7 +926,7 @@ spec:css-sizing-3; type:property; text:box-sizing
 					Where the specified values are not applied on the table grid and/or wrapper boxes,
 						the unset values are used instead for that box (inherit or initial, depending on the property).
 
-				<li>The 'overflow' property on the <a>table-root</a> and <a>table-wrapper</a> box, when its value is not either <code>visible</code> or <code>hidden</code>,
+				<li>The 'overflow' property on the <a>table-root</a> and <a>table-wrapper</a> box, when its value is not either <code>visible</code>, <code>clip</code> or <code>hidden</code>,
 					is ignored and treated as if its value was <code>visible</code>.
 
 				<li>All css properties of <a>table-column</a> and <a>table-column-group</a> boxes are ignored,