Java: add instructions to automodel query publish script

java/ql/automodel/publish.sh

@@ -1,6 +1,9 @@
 #!/bin/sh
 set -e
 
+# Before running this, make sure there is an SSO-enabled token with package:write
+# permissions to codeql supplied via the GITHUB_TOKEN environment variable
+
 AUTOMODEL_ROOT="$(readlink -f "$(dirname $0)")"
 WORKSPACE_ROOT="$AUTOMODEL_ROOT/../../.."
 GRPS="automodel,-test"