Merge pull request w3c#6013 from nschonni/css-fonts-5-images

[css-fonts-5] Remove space in image names

Author: svgeesus

css-fonts-5/Overview.bs

@@ -217,7 +217,7 @@ within an individual element e.g. for characters not supported by the primary fo
 </xmp>
     This image shows each glyph's local origin, and the natural advance between them:
     <figure>
-        <img alt="Natural advance of Helvetica glyphs" src="images/Helvetica Natural Advance.png" width="147" height="114">
+        <img alt="Natural advance of Helvetica glyphs" src="images/Helvetica_Natural_Advance.png" width="147" height="114">
     </figure>
     In this example, the natural advance is 69.328125 pixels.
 
@@ -231,7 +231,7 @@ within an individual element e.g. for characters not supported by the primary fo
 </pre>
    The rendering will look like this:
     <figure>
-        <img alt="Overridden advance of Helvetica glyphs" src="images/Helvetica Overridden Advance.png" width="176" height="112">
+        <img alt="Overridden advance of Helvetica glyphs" src="images/Helvetica_Overridden_Advance.png" width="176" height="112">
     </figure>
     In this example, the used advance between the glyphs is 69.328125 pixels * 1.4 = 97.059375 pixels.
 </div>