docs/k8s: make run.sh handle SIGINT

It was previously using jobcontrol to achieve this, but that apparently
doesn't work when there is no tty. This makes it so that it directly
handles SIGINT and SIGTERM and passes it on to tailscaled. I tested this
works on a Digital Ocean K8s cluster.

Fixes #5512

Signed-off-by: Maisem Ali <maisem@tailscale.com>
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f