[css-transforms-2] Fix use of nonexistent variable.

Fix use of the nonexistent variable dot which was meant to be product,
which was the result of calling the dot() function.

Also remove a "* 1" while I'm there.

Fixes w3c#911

Author: dbaron

css-transforms-2/Overview.bs

@@ -1170,8 +1170,8 @@ if (abs(product) == 1.0)
 	 quaternionDst = quaternionA
 	 return
 
-theta = acos(dot)
-w = sin(t * theta) * 1 / sqrt(1 - product * product)
+theta = acos(product)
+w = sin(t * theta) / sqrt(1 - product * product)
 
 for (i = 0; i < 4; i++)
 	quaternionA[i] *= cos(t * theta) - product * w