chore(deps): pin ubuntu docker tag to 561618e

Author: renovate[bot]

.cursor/Dockerfile

@@ -4,7 +4,7 @@
 # the shells the completion integration tests exercise. Repo-pinned tools
 # (declared in mise.toml) are installed after checkout by .cursor/install.sh,
 # because mise.toml is only available once the repository is cloned.
-FROM ubuntu:24.04
+FROM ubuntu:24.04@sha256:561618e2c15bf2397621dd04f96926663a3b5616c189cf7e38db7e82f5c538ea
 
 ENV DEBIAN_FRONTEND=noninteractive