Fix the data source issue

[BrianZhang2018]

In 06- regression examples:

the below data source is missing now, !wget http://www.amstat.org/publications/jse/v19n3/decock/AmesHousing.txt;

can use this instead: !wget https://jse.amstat.org/v19n3/decock/AmesHousing.txt;