Update Dockerfile to .NET 8

Dockerfile

@@ -1,7 +1,7 @@
-FROM mcr.microsoft.com/dotnet/core/runtime:5.0 AS base
+FROM mcr.microsoft.com/dotnet/runtime:8.0 AS base
 WORKDIR /app
 
-FROM mcr.microsoft.com/dotnet/core/sdk:5.0 AS build
+FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
 WORKDIR /src
 COPY ["src/Theorem/Theorem.csproj", "./"]
 RUN dotnet restore "./Theorem.csproj"
@@ -15,5 +15,4 @@ RUN dotnet publish "Theorem.csproj" -c Release -o /app/publish -p:PublishReadyTo
 FROM base AS final
 WORKDIR /app
 COPY --from=publish /app/publish .
-COPY "appsettings.json" .
-ENTRYPOINT ["dotnet", "Theorem.dll"]
+ENTRYPOINT ["dotnet", "Theorem.dll"]