readme: drop forum for discussions (#1725)

Author: bruno-garcia

README.md

@@ -81,9 +81,8 @@ For more details, please: **refer to the [documentation](https://getsentry.githu
 Sentry's [Raven SDK](https://github.com/getsentry/raven-csharp/) is still available, and recommended for use with .NET Framework 3.5 to 4.6.0.
 
 ## Resources
-
 * [![Documentation](https://img.shields.io/badge/documentation-sentry.io-green.svg)](https://docs.sentry.io/platforms/dotnet/)
-* [![Forum](https://img.shields.io/badge/forum-sentry-green.svg)](https://forum.sentry.io/c/sdks)
+* [![Discussions](https://img.shields.io/github/discussions/getsentry/sentry-dotnet.svg)](https://github.com/getsentry/sentry-dotnet/discussions)
 * [![Discord Chat](https://img.shields.io/discord/621778831602221064?logo=discord&logoColor=ffffff&color=7389D8)](https://discord.gg/PXa5Apfe7K)
 * [![Stack Overflow](https://img.shields.io/badge/stack%20overflow-sentry-green.svg)](http://stackoverflow.com/questions/tagged/sentry)
 * [![Twitter Follow](https://img.shields.io/twitter/follow/getsentry?label=getsentry&style=social)](https://twitter.com/intent/follow?screen_name=getsentry)