priv-helper: remove D-Bus Alias for "nm-priv-helper.service"

In systemd, it's common that a D-Bus activatable service references
`SystemdService=dbus-$BUSNAME.service` instead the real service name.
Together with an `[Install].Alias=dbus-$BUSNAME.service` directive,
this allowed to enable/disable D-Bus activation without uninstalling the
service altogether ([1]).

Currently, when we install the RPM then `nm-priv-helper.service` is not
enabled, consequently the alias is not created, and D-Bus activation
does not work. I guess, we should fix that by enabling the service in
the %post section or via a systemd preset? Dunno.

Anyway. It seems that nm-priv-helper.service is more of an
implementation detail of NetworkManager. It makes not sense for the user
to interact directly, or to enable/disable D-Bus activation (because
that is how it works).

So, drop the alias.

See-also: [1] https://docs.fedoraproject.org/en-US/packaging-guidelines/Systemd/#activation_dbus
(cherry picked from commit d849807521)

data/nm-priv-helper.service.in

@@ -73,7 +73,3 @@ CapabilityBoundingSet=CAP_DAC_OVERRIDE
 PrivateUsers=no
 RestrictAddressFamilies=AF_UNIX
 SystemCallFilter=@resources
-
-
-[Install]
-Alias=dbus-org.freedesktop.nm_priv_helper.service

src/nm-priv-helper/org.freedesktop.nm_priv_helper.service.in

@@ -2,4 +2,4 @@
 Name=org.freedesktop.nm_priv_helper
 Exec=@libexecdir@/nm-priv-helper
 User=root
-SystemdService=dbus-org.freedesktop.nm_priv_helper.service
+SystemdService=nm-priv-helper.service