chore(ubi9-rust-builder): Add renovate annotation

Author: Techassi

ubi9-rust-builder/Dockerfile

@@ -9,6 +9,8 @@ LABEL maintainer="Stackable GmbH"
 
 # Pin the rustup version to avoid unexpected breaking changes.
 # See https://github.com/rust-lang/rustup/blob/4514d36fcc9c42416176111cd841c86f7ec44b2c/rustup-init.sh#L91
+# Find the latest version here: https://github.com/rust-lang/rustup/blob/master/CHANGELOG.md
+# renovate: datasource=github-tags packageName=rust-lang/rustup
 ENV RUSTUP_VERSION=1.28.1
 # This SHOULD be kept in sync with operator-templating and other tools to reduce build times
 # Find the latest version here: https://doc.rust-lang.org/stable/releases.html