[css-writing-modes] Update captions on figures

Author: fantasai

css-writing-modes-3/Overview.bs

@@ -1576,12 +1576,16 @@ Flow-relative Directions</h3>
     not only on the 'writing-mode' property but also the 'direction' property.</p>
 
   <div class="example">
-    <p>An English (LTR-TB) block:</p>
-    <img src="diagrams/sizing-ltr-tb.svg">
+    <figure>
+      <img src="diagrams/sizing-ltr-tb.svg">
+      <figcaption>Physical/logical terms as applicable to typical English text layout</a>
+    </figure>
   </div>
   <div class="example">
-    <p>A vertical Japanese block (TTB-RL):</p>
-    <img src="diagrams/sizing-ttb-rl.svg">
+    <figure>
+      <img src="diagrams/sizing-ltr-tb.svg">
+      <figcaption>Physical/logical terms as applicable to typical Chinese text layout</a>
+    </figure>
   </div>
 
 <h3 id="line-directions">

css-writing-modes-4/Overview.bs

@@ -1651,12 +1651,16 @@ Flow-relative Directions</h3>
     not only on the 'writing-mode' property but also the 'direction' property.</p>
 
   <div class="example">
-    <p>An English (LTR-TB) block:</p>
-    <img src="diagrams/sizing-ltr-tb.svg">
+    <figure>
+      <img src="diagrams/sizing-ltr-tb.svg">
+      <figcaption>Physical/logical terms as applicable to typical English text layout</a>
+    </figure>
   </div>
   <div class="example">
-    <p>A vertical Japanese block (TTB-RL):</p>
-    <img src="diagrams/sizing-ttb-rl.svg">
+    <figure>
+      <img src="diagrams/sizing-ltr-tb.svg">
+      <figcaption>Physical/logical terms as applicable to typical Chinese text layout</a>
+    </figure>
   </div>
 
 <h3 id="line-directions">