Update plugins.adoc (#1438)

broken dockerfile

Author: mfreeman451

modules/ROOT/pages/kubernetes/plugins.adoc

@@ -94,7 +94,7 @@ Building a Docker container image that is based on the official Neo4j Docker ima
 [source, Dockerfile, subs=attributes]
 ----
 ARG  NEO4J_VERSION
-FROM neo4j:\{NEO4J_VERSION}
+FROM neo4j:$\{NEO4J_VERSION}
 
 # copy my-plugins into the Docker image
 COPY my-plugins/ /var/lib/neo4j/plugins
@@ -254,4 +254,4 @@ apoc_credentials: {}
 #     aliasName: "es"
 #     secretName: "essecret"
 #     secretMountPath: "/secret/esCred"
-----
+----