[css-contain-1][editorial] Move the 'possible optimizations' to non-normative subsections

Matches the corresponding change in L2 (see
cf75d0c)

Author: frivoal

css-contain-1/Overview.bs

@@ -864,6 +864,12 @@ Size Containment</h3>
 		and its [=natural height=] is treated as 0.
 	</div>
 
+
+<h4 id='containment-size-opt' class="no-toc">
+Possible Size-Containment Optimizations</h4>
+
+	<em>This section is non-normative.</em>
+
 	By itself, <a>size containment</a> does not offer much optimization opportunity.
 	Its primary benefit on its own is that tools which want to lay out the [=size containment box|containment box=]'s contents
 	based on the [=size containment box|containment box=]'s size
@@ -1044,6 +1050,11 @@ Layout Containment</h3>
 		contain-layout-baseline-005.html
 		</wpt>
 
+<h4 id='containment-layout-opt' class="no-toc">
+Possible Layout-Containment Optimizations</h4>
+
+	<em>This section is non-normative.</em>
+
 	Possible optimizations that can be enabled by <a>layout containment</a> include (but are not limited to):
 
 	1. When laying out the page,
@@ -1160,7 +1171,11 @@ Paint Containment</h3>
 	contain-paint-baseline-001.html
 	</wpt>
 
-<div class=informative>
+<h4 id='containment-paint-opt' class="no-toc">
+Possible Paint-Containment Optimizations</h4>
+
+	<em>This section is non-normative.</em>
+
 	Possible optimizations that can be enabled by <a>paint containment</a> include (but are not limited to):
 
 	1. If the [=paint containment box|containment box=] is off-screen or obscured,
@@ -1186,7 +1201,6 @@ Paint Containment</h3>
 
 	3. Because they are guaranteed to be stacking contexts,
 		scrolling elements can be painted into a single GPU layer.
-</div>
 
 Privacy and Security Considerations {#priv-sec}
 ==============================================