Replace `DOTNET_SKIP_FIRST_TIME_EXPERIENCE` with `DOTNET_NOLOGO`

`DOTNET_SKIP_FIRST_TIME_EXPERIENCE` was completely removed in .NET Core 3.0 and `DOTNET_NOLOGO` was reintroduced as its replacement in .NET Core 3.1 to only suppress the First Time Use Experience message. cc: @daxian-dbw See https://learn.microsoft.com/en-us/dotnet/core/tools/dotnet-environment-variables#dotnet_nologo for details.