Reducing the kubespray version from 2.19 to 2.18

Change-Id: Iba5e0b6ff71a512b13d8cb9733c9356abdaf439a
diff --git a/Makefile b/Makefile
index 0ff5609..fb72770 100644
--- a/Makefile
+++ b/Makefile
@@ -21,7 +21,7 @@
 TEST_APP_VALUES      ?= $(MAKEDIR)/5g-test-apps-values.yaml
 GET_HELM              = get_helm.sh
 
-KUBESPRAY_VERSION ?= release-2.19
+KUBESPRAY_VERSION ?= release-2.18
 DOCKER_VERSION    ?= '20.10'
 HELM_VERSION	  ?= v3.10.3
 KUBECTL_VERSION   ?= v1.23.15