[2.0.72] braking_force and friction_force aren't searchable

[BurninSun]

Searching the prototype docs for braking_force (braking_power) or friction_force (friction) do not give any results since those properties are listed as an "either/or" property and are not the primary.
Those should still show up in the search results and lead to the same link as the primary property.

[Bilka]

This is solved for 2.1.