core/unit: drop unneeded unit_modify_nft_set() call during coldplug

We re-realize all unit cgroups upon daemon-reload, and
cgroup_context_apply() would take care of NFT set refreshing.
No need to duplicate that in unit_coldplug().

src/core/cgroup.c

@@ -1325,7 +1325,7 @@ static void cgroup_apply_firewall(Unit *u) {
         (void) bpf_firewall_install(u);
 }
 
-void unit_modify_nft_set(Unit *u, bool add) {
+static void unit_modify_nft_set(Unit *u, bool add) {
         int r;
 
         assert(u);

src/core/cgroup.h

@@ -379,8 +379,6 @@ int cgroup_context_add_device_allow(CGroupContext *c, const char *dev, CGroupDev
 int cgroup_context_add_or_update_device_allow(CGroupContext *c, const char *dev, CGroupDevicePermissions p);
 int cgroup_context_add_bpf_foreign_program(CGroupContext *c, uint32_t attach_type, const char *path);
 
-void unit_modify_nft_set(Unit *u, bool add);
-
 CGroupMask unit_get_own_mask(Unit *u);
 CGroupMask unit_get_delegate_mask(Unit *u);
 CGroupMask unit_get_members_mask(Unit *u);

src/core/unit.c

@@ -3801,7 +3801,6 @@ int unit_coldplug(Unit *u) {
         if (u->nop_job)
                 RET_GATHER(r, job_coldplug(u->nop_job));
 
-        unit_modify_nft_set(u, /* add= */ true);
         return r;
 }