[css-contain] fix typo

Author: frivoal

css-contain-1/Overview.bs

@@ -281,7 +281,7 @@ Strong Containment: the 'contain' property</h2>
 		<dt><dfn>paint</dfn>
 		<dd>
 			This value turns on <a>paint containment</a> for the element.
-			This ensures that the descendants of the [=paint containment box|containment box] don't display outside its bounds,
+			This ensures that the descendants of the [=paint containment box|containment box=] don't display outside its bounds,
 			so if an element is off-screen or otherwise not visible,
 			its descendants are also guaranteed to be not visible.
 
@@ -795,11 +795,11 @@ Layout Containment</h3>
 		as they're guaranteed not to affect each other.
 
 	2. When laying out the page,
-		if the [=layout containment box|containment box] is off-screen or obscured
+		if the [=layout containment box|containment box=] is off-screen or obscured
 		and the layout of the visible parts of the screen do not depend on the size of the [=layout containment box|containment box=]
 		(for example, if the [=layout containment box|containment box=] is near the end of a block container,
 		and you're viewing the beginning of the block container),
-		the layout of the [=layout containment box|containment box]' contents can be delayed or done at a lower priority.
+		the layout of the [=layout containment box|containment box=]' contents can be delayed or done at a lower priority.
 
 		(When paired with <a>size containment</a>,
 		this optimization can be applied more liberally.)

css-contain-2/Overview.bs

@@ -329,7 +329,7 @@ Strong Containment: the 'contain' property</h2>
 		<dt><dfn>paint</dfn>
 		<dd>
 			This value turns on <a>paint containment</a> for the element.
-			This ensures that the descendants of the [=paint containment box|containment box] don't display outside its bounds,
+			This ensures that the descendants of the [=paint containment box|containment box=] don't display outside its bounds,
 			so if an element is off-screen or otherwise not visible,
 			its descendants are also guaranteed to be not visible.
 
@@ -818,11 +818,11 @@ Layout Containment</h3>
 		as they're guaranteed not to affect each other.
 
 	2. When laying out the page,
-		if the [=layout containment box|containment box] is off-screen or obscured
+		if the [=layout containment box|containment box=] is off-screen or obscured
 		and the layout of the visible parts of the screen do not depend on the size of the [=layout containment box|containment box=]
 		(for example, if the [=layout containment box|containment box=] is near the end of a block container,
 		and you're viewing the beginning of the block container),
-		the layout of the [=layout containment box|containment box]' contents can be delayed or done at a lower priority.
+		the layout of the [=layout containment box|containment box=]' contents can be delayed or done at a lower priority.
 
 		(When paired with <a>size containment</a>,
 		this optimization can be applied more liberally.)