gpu: update definition of path vertex size

The size is unchanged, but a corner is no longer encoded as two
16-bit ints (2*2 bytes); it is encoded as a float32 (1*4 bytes).

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/path.go

@@ -143,7 +143,7 @@ const (
 	// Number of path quads per draw batch.
 	pathBatchSize = 10000
 	// Size of a vertex as sent to gpu
-	vertStride = 7*4 + 2*2
+	vertStride = 8 * 4
 )
 
 func newPather(ctx backend.Device) *pather {