[css-transforms-1] Remove closed issue from spec text.

Author: dirkschulze

css-transforms-1/Overview.bs

@@ -1158,8 +1158,6 @@ The pseudo code below is based upon the "unmatrix" method in "Graphics Gems II,
 
 Matrices in the pseudo code use the column-major order. The first index on a matrix entry represents the column and the second index represents the row.
 
-Issue(w3c/csswg-drafts#483): Incorrect indices for matrix?
-
 <pre>
 Input:  matrix      ; a 4x4 matrix
 Output: translation ; a 2 component vector