removed non-existing nuget urls to pass the markdown lint check

Author: Yun-Ting

src/OpenTelemetry.Exporter.Prometheus.AspNetCore/README.md

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 # Prometheus Exporter AspNetCore for OpenTelemetry .NET
 
-[![NuGet](https://img.shields.io/nuget/v/OpenTelemetry.Exporter.Prometheus.AspNetCore.svg)](https://www.nuget.org/packages/OpenTelemetry.Exporter.Prometheus.AspNetCore)
-[![NuGet](https://img.shields.io/nuget/dt/OpenTelemetry.Exporter.Prometheus.AspNetCore.svg)](https://www.nuget.org/packages/OpenTelemetry.Exporter.Prometheus.AspNetCore)
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 An [OpenTelemetry Prometheus exporter](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk_exporters/prometheus.md) for configuring an ASP.NET Core application with an endpoint for Prometheus to scrape.
 
 ## Prerequisite

src/OpenTelemetry.Exporter.Prometheus.HttpListener/README.md

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 # Prometheus Exporter HttpListener for OpenTelemetry .NET
 
-[![NuGet](https://img.shields.io/nuget/v/OpenTelemetry.Exporter.Prometheus.HttpListener.svg)](https://www.nuget.org/packages/OpenTelemetry.Exporter.Prometheus.HttpListener)
-[![NuGet](https://img.shields.io/nuget/dt/OpenTelemetry.Exporter.Prometheus.HttpListener.svg)](https://www.nuget.org/packages/OpenTelemetry.Exporter.Prometheus.HttpListener)
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 An [OpenTelemetry Prometheus exporter](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk_exporters/prometheus.md) that configures an [HttpListener](https://docs.microsoft.com/dotnet/api/system.net.httplistener) instance for Prometheus to scrape.
 
 ## Prerequisite