[css-ruby-1] Fix spelling

Author: fantasai

css-ruby-1/Overview.bs

@@ -761,7 +761,7 @@ White Space Collapsing</h3>
 		They also ensure that annotated white space is preserved. For example,
 		<pre highlight=html>
 			&lt;ruby>
-				&lt;rb>Aerith&lt;/rb>&lt;rb> &lt;/rb>&lt;rb>Gainsboro&lt;/rb>
+				&lt;rb>Aerith&lt;/rb>&lt;rb> &lt;/rb>&lt;rb>Gainsborough&lt;/rb>
 				&lt;rt>エアリス&lt;/rt>&lt;rt>・&lt;/rt>&lt;rt>ゲインズブール&lt;/rt>
 			&lt;/ruby></pre>
 	</div>