[SDL 0285] ShowConstantTBT Description Update

[theresalech]

Proposal: ShowConstantTBT Description Update

This proposal is to update the descriptions of ShowConstantTBT's parameters distanceToManeuver and distanceToManeuverScale so we get consistent use of them across all OEMs and Navigation apps.

Review: smartdevicelink/sdl_evolution#955

The following comments need to be updated:

• ShowConstantTBT.distanceToManeuver
• ShowConstantTBT.distanceToManeuverScale

[crokita]

The changes are included in the project