Mark docker.image.virtualsize deprecated (#6016)

This is deprecated in the SDK and is replaced with size which we already
use

Signed-off-by: Tim Smith <tsmith84@gmail.com>

Author: tas50

providers/os/resources/os.lr

@@ -969,7 +969,7 @@ docker.image {
   id string
   // Image size in kilobytes
   size int
-  // Virtual image size in kilobytes
+  // Virtual image size in kilobytes. Deprecated; use size instead
   virtualsize int
   // Tag key value pairs
   tags []string