action-scripts.h: rm explicit numbering of enum

C standard specifies that the first enum element is 0 and the next ones
are +1 to a previous element (C90, "3.5.2.2 Enumeration specifiers").
Therefore, there is no need to explicitly specify element values.

The explicit initializers were added in commit 56763837 (scripts:
Add ACT_MAX limit and make @action_names being const) but I do not
see the need for them in there either.

No functional change.

Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>