Merge pull request #4053 from lahmatiy/patch-6

[css-transforms-2] Simplify matrix3d() syntax

Author: tabatkins

css-transforms-2/Overview.bs

@@ -880,7 +880,7 @@ In the following <dfn export>3d transform functions</dfn>, a <<zero>> behaves th
 ("Unitless 0" angles are preserved for legacy compat reasons.)
 
 
-: <span class='prod'><dfn>matrix3d()</dfn> = matrix3d( <<number>> [, <<number>> ]{15,15} )</span>
+: <span class='prod'><dfn>matrix3d()</dfn> = matrix3d( <<number>>#{16} )</span>
 :: specifies a 3D transformation as a 4x4 homogeneous matrix of 16 values in column-major order.
 : <span class='prod'><dfn>translate3d()</dfn> = translate3d( <<length-percentage>> , <<length-percentage>> , <<length>> )</span>
 :: specifies a <a href="#Translate3dDefined">3D translation</a> by the vector [tx,ty,tz], with tx, ty and tz being the first, second and third translation-value parameters respectively.