Reference explicit framework version in docker file

Dockerfile

@@ -3,7 +3,7 @@ WORKDIR /scip-dotnet
 ADD . /scip-dotnet
 RUN dotnet pack
 ENV PATH="/root/.dotnet/tools:${PATH}"
-RUN dotnet tool install --add-source ScipDotnet/bin/Release/ --global scip-dotnet
+RUN dotnet tool install --framework net8.0 --add-source ScipDotnet/bin/Release/ --global scip-dotnet
 RUN dotnet clean
 WORKDIR /app
 RUN rm -rf /scip-dotnet