Replace dhclient dependency with dhcp-client

Description:

Upstream commit 6d61b63 (2024-02) made "dhcpcd the default dhcp client".

cloud-init 23.3 had added support for "busybox micro DHCP (udhcpc) alternative to deprecated isc-dhcp-client".

The Debian package accepts dhcpcd, udhcpc or isc-dhcp-client as dhcp-client provider (see also their Bug#1051421: "cloud-init: Avoid hard dependency on isc-dhcp-client").

This would remove the last hard dep on the deprecated/EOL dhclient from our repos.

Additional info:

• package version(s): 24.3.1-3
• link to upstream bug report, if any: https://github.com/canonical/cloud-init/pull/4912