Revise Safety Impact decision point for better integration with generated documentation

[ahouseholder]

docs/_generated/decision_points/safety_impact_1_0_0.md looks less good than the SSVC v2.0 PDF, because the table there was structured very differently than the other decision points. It has these sub-categories of physical harm, psychological harm, etc. And I think these are, predictably, printing in a way that is confusing.

I propose we make a new issue to attempt a re-write of the safety impact decision point to make the text more amenable to being consistent with our more automated design and document management process. The code does what is expected given the text for safety impact. So it's not a problem with this PR.

Originally posted by @j--- in #370 (comment)

[ahouseholder]

This issue depends on

• Realign Safety DPs with IEC 61508? #311
• Realign Safety decision points IEC 61508 #439

insofar as the resolution of the present issue should be built on the changes in #439 rather than starting from the main branch as of this writing. Once #439 merges, this issue should be clear to proceed.

[ahouseholder]

• make safety table formats look better #479 provided a cosmetic fix for this issue, but resulted in
• Strip HTML out of python decision point values when rendering decision points to json #483 as future technical debt
• Revise Safety decision point value text #482 is a follow-on task that addresses the content revision aspect of this issue more directly