generate-docker-compose: Clean up the container afterwards

I'll never understand why this isn't the default, docker.

generate-docker-compose

@@ -4,7 +4,7 @@ set -eu
 
 # We generate first, and capture the output, to avoid overwriting the file on error.
 # To avoid jsonnet needing to exist locally, we run it in a container.
-output=$(docker run -i sparkprime/jsonnet - < docker-compose.jsonnet)
+output=$(docker run --rm -i sparkprime/jsonnet - < docker-compose.jsonnet)
 
 {
 	echo "# DO NOT EDIT THIS FILE!"