Disable being able to edit code while debugging

According to the VS Team this works as designed:

This behavior you described is expected for Visual Studio 16.3. We went through several changes on Edit and Continue and now allow editing the code while the application is running. Any errors or warnings regarding your changes will show up at the Error List Window. In order to apply these changes, you simply have to be on a break state (e.g. break all or stop on a breakpoint) and continue from there.

Source: https://developercommunity.visualstudio.com/content/problem/768979/able-to-type-while-debugging.html