jetbrains.rider: bump dotnet sdk

Jetbrains have upgraded their internal runtime to .NET 6.
This can be checked by executing a command in the original package:
`strings lib/ReSharperHost/linux-x64/dotnet/dotnet | grep "Version "`

pkgs/applications/editors/jetbrains/default.nix

@@ -1,6 +1,6 @@
 { lib, stdenv, callPackage, fetchurl
 , jdk, cmake, gdb, zlib, python3
-, dotnet-sdk_5
+, dotnet-sdk_6
 , maven
 , autoPatchelfHook
 , libdbusmenu
@@ -210,7 +210,7 @@ let
       postPatch = lib.optionalString (!stdenv.isDarwin) (attrs.postPatch + ''
         rm -rf lib/ReSharperHost/linux-x64/dotnet
         mkdir -p lib/ReSharperHost/linux-x64/dotnet/
-        ln -s ${dotnet-sdk_5}/bin/dotnet lib/ReSharperHost/linux-x64/dotnet/dotnet
+        ln -s ${dotnet-sdk_6}/bin/dotnet lib/ReSharperHost/linux-x64/dotnet/dotnet
       '');
     });