Readme Related Repositories sections should link to the aspire-dashboard repo

[MichaelSimons]

They do in the nightly repos but not in the official repos. This is because of a condition in the template for when aspire-dashboard was only available in nightly

From https://raw.githubusercontent.com/dotnet/dotnet-docker/main/eng/readme-templates/RelatedRepos.md:

}}{{if isNightlyRepo && SHORT_REPO != "aspire-dashboard"
    :* [dotnet/nightly/aspire-dashboard]({{InsertTemplate("Url.md", [ "readme-host": ARGS["readme-host"], "repo": "dotnet/nightly/aspire-dashboard" ])}}): .NET Aspire Dashboard (Preview)
}}

[lbussell]

Related: #5348

[MichaelSimons]

This can't be done in Docker Hub yet because of #5415