Correction in the linkerd documentation

[Chakki1301]

https://linkerd.io/2.12/tasks/using-ingress/#traefik-2x - Traefik 2.x ingressroute middleware should be in emojivoto namespace instead of traefik namespace. Thanks.

[mateiidavid]

@Chakki1301 would you be up for submitting a PR in our website repository with the change?