Update DotNet Support links (#10145)

README.md

@@ -109,9 +109,9 @@ You can also download the PowerShell binary archives for Windows, macOS and Linu
 [in-tar-macos]: https://docs.microsoft.com/powershell/scripting/setup/installing-powershell-core-on-macos?view=powershell-6#binary-archives
 [in-raspbian]: https://docs.microsoft.com/powershell/scripting/setup/installing-powershell-core-on-linux?view=powershell-6#raspbian
 [in-arm]: https://docs.microsoft.com/powershell/scripting/setup/powershell-core-on-arm?view=powershell-6
-[corefx-win]:https://github.com/dotnet/core/blob/master/release-notes/2.1/2.1-supported-os.md#windows
-[corefx-linux]:https://github.com/dotnet/core/blob/master/release-notes/2.1/2.1-supported-os.md#linux
-[corefx-macos]:https://github.com/dotnet/core/blob/master/release-notes/2.1/2.1-supported-os.md#macos
+[corefx-win]:https://github.com/dotnet/core/blob/master/release-notes/3.0/3.0-supported-os.md#windows
+[corefx-linux]:https://github.com/dotnet/core/blob/master/release-notes/3.0/3.0-supported-os.md#linux
+[corefx-macos]:https://github.com/dotnet/core/blob/master/release-notes/3.0/3.0-supported-os.md#macos
 
 To install a specific version, visit [releases](https://github.com/PowerShell/PowerShell/releases).