Replace DOTNET_SKIP_FIRST_TIME_EXPERIENCE with DOTNET_NOLOGO

[xtqqczze]

Suppress First Time Use Experience message in CI logs.

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.