cloud/shepherd/provider/equinix: fix wrong usage of slices.DeleteFunc

Change-Id: I736dc4ebde844d602ea84c5660c583e881538b16
Reviewed-on: https://review.monogon.dev/c/monogon/+/3041
Tested-by: Jenkins CI
Reviewed-by: Serge Bazanski <serge@monogon.tech>
diff --git a/cloud/shepherd/provider/equinix/provider.go b/cloud/shepherd/provider/equinix/provider.go
index ebd9699..f642eaf 100644
--- a/cloud/shepherd/provider/equinix/provider.go
+++ b/cloud/shepherd/provider/equinix/provider.go
@@ -241,7 +241,7 @@
 	}
 	klog.Infof("Created a new device within Equinix (RID: %s, PID: %s, HOST: %s)", rsv.ID, nd.ID, hostname)
 
-	slices.DeleteFunc(ep.reservationCache, func(v packngo.HardwareReservation) bool {
+	ep.reservationCache = slices.DeleteFunc(ep.reservationCache, func(v packngo.HardwareReservation) bool {
 		return rsv.ID == v.ID
 	})