No Figure 7 in Endpoint to Endpoint Messages section

[daidoji]

Similarly with #25 there's a Figure 7 listed in (Section 5.4)[https://trustoverip.github.io/tswg-tsp-specification/#endpoint-to-endpoint-messages] that doesn't seem to exist in the codebase.

Also note that like #25 this issue is related to the image not existing anywhere (that I can find it anyways) and not necessarily the fix that already went in for images in general in #19 to fix #15