[css-grid-2] Add missed partial marker

Author: lahmatiy

css-grid-2/Overview.bs

@@ -98,7 +98,7 @@ Establishing a Subgrid</h3>
 	<a>Subgrids</a> provide the ability to pass grid parameters down through nested elements,
 	and content-based sizing information back up to their parent grid.
 
-	<pre class="propdef">
+	<pre class="propdef partial">
 	Name: grid-template-rows, grid-template-columns
 	New values: subgrid <<line-name-list>>?
 	</pre>
@@ -697,7 +697,7 @@ Aspect-ratio&ndash;controlled Gutters</h2>
 	Note this feature is likely to move to css-align-4,
 	it is just being drafted up here while css-align-3 stabilizes.
 
-	<pre class="propdef">
+	<pre class="propdef partial">
 	Name: align-content, justify-content
 	New values: [ <<transfer-ratio>> <<content-distribution>>? ]
 	</pre>