[Prometheus.HttpListener] Remove UriPrefixes from .NET documentation

[martincostello]

The Configure the example app to use OpenTelemetry's Prometheus exporter on learn.microsoft.com uses the following code snippet:

.AddPrometheusHttpListener(options => options.UriPrefixes = new string[] { "http://localhost:9184/" })

The UriPrefixes property was made obsolete in #7114.

Once we have released a version containing this change to NuGet.org we should update the samples (1, 2) to use Host and Port instead.

[Kielek]

I think that you can do even without release. Documentation should be considered as versioned. Nuget packages should include statis links by commits/tags.

[martincostello]

Their samples' code is checked in CI, so without a package the PR would fail to compile and couldn't be merged.

[Kielek]

Missed that it is for external repo. Sorry.