[AI] Navmesh generates incorrect triangles that connect a lower platform to one above it

Navmesh is setting some vertices to be quite above what would be the max step height of the agent when two platforms are aligned with one above the other. The navmesh may reach up to the upper platform, but it does not connect the two regions.

The navmesh goes to an expected state if Region Partitioning is set to use Chunky Monotone. It also will work as expected if the Mark Low Height Areas flag is enabled.

1. Open attached project
2. Load the JB_Testmap level in the Maps folder
3. Move the narrow, lower platform slowly along the X-axis so the navmesh can automatically rebuild

Expected Result: The navmesh builds to stay with the lower platform and no connection to the upper platform is made.

Actual Result: The navmesh builds triangles that extend from the bottom platform to the top platform but do not make a connection with the navmesh area on the top platform.