Fix router version in readme.md

[0xoldhu]

From readme the router_version still links to images. But from the docs it points to release page. So it needs to be fixed to help routers set up the latest release version.

[dharmendrakariya]

also there is discrepancy in docker image name, in docker-compose its coming from here ghcr.io/connext/router:latest while in docs as you said it mentions from ghcr.io/connext/nxtp-router:latest

[rhlsthrm]

also there is discrepancy in docker image name, in docker-compose its coming from here ghcr.io/connext/router:latest while in docs as you said it mentions from ghcr.io/connext/nxtp-router:latest

This discrepancy is coming from the legacy -> amarok change. The legacy branch reflects the old versions.