Do not copy nuget.config.

Dockerfile

@@ -7,9 +7,6 @@ ARG SQUIDEX__VERSION=4.0.0
 
 WORKDIR /src
 
-# Copy nuget project files.
-COPY backend/*.sln backend/NuGet.Config  ./
-
 # Copy the main source project files
 COPY backend/src/*/*.csproj ./
 RUN for file in $(ls *.csproj); do mkdir -p src/${file%.*}/ && mv $file src/${file%.*}/; done