[css-fonts-4] Use 14deg instead of 20deg as default oblique angle per WG resolution. w3c#2295

Author: fantasai

css-fonts-4/Overview.bs

@@ -649,7 +649,7 @@ Font style: the 'font-style!!property' property</h3>
             Controls matching against an oblique face.
             Positive angles represent a clockwise slant;
             negative angles represent a counter-clockwise slant.
-            The lack of an <<angle>> represents ''20deg''.
+            The lack of an <<angle>> represents ''14deg''.
             (Note that a font might internally provide its own mapping for "oblique",
             but the mapping within the font is disregarded.)
             Fractional and negative values are accepted; however,