Fix versioning in K8s makefile (elastic#3256)

* try to get builds running

* change doc-version

* update k8s file

* fix makefile version fetch

* fix typo

* fix cut command

* Revert change to version file

* tinkering with version strings

* change daemonset template

deploy/kubernetes/Makefile

@@ -1,7 +1,7 @@
 ALL=elastic-agent-standalone elastic-agent-managed
 
 BEAT_VERSION=$(shell grep '^:stack-version:' ../../version/docs/version.asciidoc | cut -c 17- )
-BRANCH_VERSION=$(shell grep '^:doc-branch:' ../../version/docs/version.asciidoc | cut -c 14- )
+BRANCH_VERSION=$(shell grep '^:stack-version:' ../../version/docs/version.asciidoc | cut -c 17- )
 
 #variables needed for ci-create-kubernetes-templates-pull-request
 ELASTIC_AGENT_REPO=kibana
@@ -117,4 +117,4 @@ $(ALL):
 else
 	echo "No KSM templates generated. Please run: GENERATEKUSTOMIZE=true make ci-create-kustomize "
 
-endif
+endif