chore(txsim): removes deprecated `-r` flag from txsim docker README #7231

Job	Run time
docker-security-build / prepare-env	4s
docker-txsim-build / prepare-env	5s
docker-security-build / logic-check	1s
docker-txsim-build / logic-check	1s
docker-security-build / docker-security	1m 55s
docker-txsim-build / docker-security	1m 57s
docker-security-build / docker-build (DockerHub; docker.io/celestiaorg/celestia-app)	5s
docker-security-build / docker-build (GHCR; ghcr.io/celestiaorg/celestia-app)	2m 6s
docker-security-build / docker-build (ScaleWay; rg.fr-par.scw.cloud/celestiaorg/celestia-app)	3s
docker-txsim-build / docker-build (DockerHub; docker.io/celestiaorg/txsim)	4s
docker-txsim-build / docker-build (GHCR; ghcr.io/celestiaorg/txsim)	1m 55s
docker-txsim-build / docker-build (ScaleWay; rg.fr-par.scw.cloud/celestiaorg/txsim)	4s
	8m 20s

Provide feedback