chore(txsim): removes deprecated `-r` flag from txsim docker README #7251

Job	Run time
docker-txsim-build / prepare-env	7s
docker-security-build / prepare-env	4s
docker-security-build / logic-check	1s
docker-txsim-build / logic-check	1s
docker-security-build / docker-security	1m 53s
docker-txsim-build / docker-security	1m 56s
docker-security-build / docker-build (DockerHub; docker.io/celestiaorg/celestia-app)	6s
docker-security-build / docker-build (GHCR; ghcr.io/celestiaorg/celestia-app)	2m 2s
docker-security-build / docker-build (ScaleWay; rg.fr-par.scw.cloud/celestiaorg/celestia-app)	6s
docker-txsim-build / docker-build (DockerHub; docker.io/celestiaorg/txsim)	5s
docker-txsim-build / docker-build (GHCR; ghcr.io/celestiaorg/txsim)	2m 5s
docker-txsim-build / docker-build (ScaleWay; rg.fr-par.scw.cloud/celestiaorg/txsim)	8s
	8m 34s

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