matrix/mat64: remove unused const
@@ -208,7 +208,6 @@ func rectanglesOverlap(off, aCols, bCols, stride int) bool {
// Flatten the shifted matrix column positions
// so a starts at 0, modulo the common stride.
- const aFrom = 0
aTo := aCols
// The mod stride operations here make the from
// and to indexes comparable between a and b when
