Reduce wording on Threat Modeling

[jgadsden]

Describe what change you would like :
The section on Threat Modeling maybe goes on a bit too long, there are several other sources that describe threat modeling better than this section. The DevGuide seeks to be a 'Lonely Planet' guide rather than a providing in-depth on any one subject, and this section is more than just a brief introduction to the subject

It would be good to revise the section on threat modeling so it is shorter and to the point
the intention there is to cut the length down by 50% or so, because really it is repeating content from the Threat Model project and the Threat Modeling Cheat Sheet

Context :
Section: 04-design/01-threat-modeling/01-threat-modeling

[jgadsden]

This has been brought over from the previous repo: Make section on Threat Modeling more brief #344