fix docker notes

Signed-off-by: Adrian Cole <[email protected]>

docker/Dockerfile

@@ -17,7 +17,9 @@
 # Use latest version here: https://github.com/orgs/openzipkin/packages/container/package/java
 # This is defined in many places because Docker has no "env" script functionality unless you use
 # docker-compose: When updating, update everywhere.
-ARG java_version=21.0.1_p12
+#
+# TODO: temporarily 11 until we can update to spark on scala 2.13
+ARG java_version=11.0.21_p9
 
 # We copy files from the context into a scratch container first to avoid a problem where docker and
 # docker-compose don't share layer hashes https://github.com/docker/compose/issues/883 normally.