Update tutorials pub-sub csharp-subscriber image to dotnet 8.0 (dapr#1001)

* Update tutorials pub-sub csharp-subscriber image to dotnet 8.0

Signed-off-by: Anton Troshin <[email protected]>

* Update Dockerfile

Signed-off-by: Artur Souza <[email protected]>

---------

Signed-off-by: Anton Troshin <[email protected]>
Signed-off-by: Artur Souza <[email protected]>
Co-authored-by: Artur Souza <[email protected]>

Author: antontroshin

tutorials/pub-sub/csharp-subscriber/Dockerfile

@@ -1,7 +1,6 @@
 # Note: we cannot do a staged dotnet docker build here for arm/arm64. 
 
-# Build runtime image
-FROM mcr.microsoft.com/dotnet/aspnet:7.0
+FROM mcr.microsoft.com/dotnet/aspnet:8.0
 WORKDIR /app
 COPY  /out .
-ENTRYPOINT ["dotnet", "csharp-subscriber.dll"]
+ENTRYPOINT ["dotnet", "csharp-subscriber.dll"]