Run acc tests against 9.0.0

Author: dimuon

Makefile

@@ -16,7 +16,7 @@ SWAGGER_VERSION ?= 8.7
 
 GOVERSION ?= $(shell grep -e '^go' go.mod | cut -f 2 -d ' ')
 
-STACK_VERSION ?= 8.15.5
+STACK_VERSION ?= 9.0.0-SNAPSHOT
 
 ELASTICSEARCH_NAME ?= terraform-elasticstack-es
 ELASTICSEARCH_ENDPOINTS ?= http://$(ELASTICSEARCH_NAME):9200