[css-ruby] minor grammer correction

Author: kojiishi

css-ruby/Overview.html

@@ -1284,7 +1284,7 @@ <h2 id=rubyover><span class=secno>4. </span> Ruby Overhang and Edge
      box</i></a> may partially overhang adjacent boxes.
 
     <p> This level of the specificaiton does not define how much the overhang
-     may be allowed under what conditions.
+     may be allowed, and under what conditions.
 
     <div class=example>
      <p> The user agent may use <a href="#JIS4051"

css-ruby/Overview.src.html

@@ -904,7 +904,7 @@ <h2 id="rubyover">
 	</p>
 	<p>
 		This level of the specificaiton does not define
-		how much the overhang may be allowed under what conditions.
+		how much the overhang may be allowed, and under what conditions.
 	</p>
 	<div class="example">
 	<p>