TT#100201 Include zstd in ngcp-services-{ce,pro}

systemd-coredump in systemd versions >=246 uses zstd as the default.
Now having 247.1-3 in current Debian/bullseye, we should have zstd
available out-of-the-box for dealing with compressed coredump files
(which are zstd by default). Given that zstd is available also in
Debian/buster, let's add it to ngcp-services-{ce,pro}.

Change-Id: I7fddd253c93f32ec7cb8f38900feab73218b2cf9

debian/control

@@ -372,6 +372,7 @@ Depends:
  systemd-coredump,
  systemd-sysv,
  systemd-timesyncd | systemd,
+ zstd,
  ${misc:Depends},
 Provides:
  ngcp-services,
@@ -457,6 +458,7 @@ Depends:
  systemd-coredump,
  systemd-sysv,
  systemd-timesyncd | systemd,
+ zstd,
  ${misc:Depends},
 Provides:
  ngcp-services,