use hal_bootctl_server in neverallow rule

Hals have 3 attributes associated with them, the attribute itself, the
_client attribute, and the _server attribute. Only the server attribute
isn't expanded using the expandattribute keyword, and as a result, is
the only attribute which can be used in neverallow rules.

Fix neverallow rule to use hal_bootctl_server, which is not expanded,
instead of hal_bootctl.

Introduced in: https://android-review.googlesource.com/c/platform/system/sepolicy/+/777178

Test: policy compiles
Bug: 119500144
Change-Id: I8cff9cc03f4c30704175afb203c68f237fbd61ca