Previous versions of Visual Studio Code can be downloaded here:
https://code.visualstudio.com/updates/
Pick the version you want from the list on the left, and then click on the download link for your OS as shown here:
You should disable auto update (as mentioned by Gregory in the comment) to prevent it from auto updating itself later upon restart. To do this, go to Preferences, Settings and then search for 'update'. Set it to 'none' as shown below:
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…