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 <anton@diagrid.io>

* Update Dockerfile

Signed-off-by: Artur Souza <asouza.pro@gmail.com>

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Signed-off-by: Anton Troshin <anton@diagrid.io>
Signed-off-by: Artur Souza <asouza.pro@gmail.com>
Co-authored-by: Artur Souza <asouza.pro@gmail.com>

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"]