[css-writing-modes] Fixed a validator issue

Author: kojiishi

css-writing-modes/Overview.bs

@@ -892,7 +892,7 @@ Introduction to Baselines</h3>
 
   <div class="figure">
     <p><img alt="Picture of alphabetic text in two font sizes with the baseline and em-boxes"
-            width="60%"
+            width="480"
             src="alphabetic-baseline-in-two-font-sizes.svg"></p>
     <p class="caption">Alphabetic text in two font sizes with the baseline and em-boxes</p>
   </div>

css-writing-modes/Overview.html

@@ -994,7 +994,7 @@ <h3 class="heading settled heading" data-level=4.1 id=intro-baselines><span clas
     the alignment of glyphs from different fonts or font sizes when typesetting.
 
   <div class=figure>
-    <p><img alt="Picture of alphabetic text in two font sizes with the baseline and em-boxes" src=alphabetic-baseline-in-two-font-sizes.svg width=60%></p>
+    <p><img alt="Picture of alphabetic text in two font sizes with the baseline and em-boxes" src=alphabetic-baseline-in-two-font-sizes.svg width=480></p>
     <p class=caption>Alphabetic text in two font sizes with the baseline and em-boxes</p>
   </div>