Cleanup: remove comment for O_DIRECT in animation playback loading

This flag isn't used, even going back to the initial commit.

source/blender/windowmanager/intern/wm_playanim.c

@@ -678,17 +678,6 @@ static void build_pict_list_ex(
     pupdate_time();
     ptottime = 1.0;
 
-    /* O_DIRECT
-     *
-     * If set, all reads and writes on the resulting file descriptor will
-     * be performed directly to or from the user program buffer, provided
-     * appropriate size and alignment restrictions are met. Refer to the
-     * F_SETFL and F_DIOINFO commands in the fcntl(2) manual entry for
-     * information about how to determine the alignment constraints.
-     * O_DIRECT is a Silicon Graphics extension and is only supported on
-     * local EFS and XFS file systems.
-     */
-
     while (IMB_ispic(filepath) && totframes) {
       bool has_event;
       size_t size;