Update RollOffMode.yaml to explain what distance is

Fix to explain what `distance` is, in reference to #935 (comment)

Author: RedrcknRbn

content/en-us/reference/engine/enums/RollOffMode.yaml

@@ -16,15 +16,17 @@ items:
     summary: |
       Volume attenuates from `Class.Sound.RollOffMinDistance` in an inverse
       manner. This option mirrors how sounds attenuate in the real world.
-      This is done through `Class.Sound.RollOffMinDistance`/`Distance`
+      This is done through `Class.Sound.RollOffMinDistance`/`distance`,
+      where `distance` is the `Datatype.Vector3.Magnitude` between the audio source and the audio listener.
     value: 0
     tags: []
     deprecation_message: ''
   - name: Linear
     summary: |
       Volume attenuates between `Class.Sound.RollOffMinDistance` and
       `Class.Sound.RollOffMaxDistance` with a linear relationship.
-      This is done through (`Class.Sound.RollOffMaxDistance`/`Distance`)/(`Class.Sound.RollOffMaxDistance`-`Class.Sound.RollOffMinDistance`)
+      This is done through (`Class.Sound.RollOffMaxDistance`/`distance`)/(`Class.Sound.RollOffMaxDistance`-`Class.Sound.RollOffMinDistance`),
+      where `distance` is the `Datatype.Vector3.Magnitude` between the audio source and the audio listener.
     value: 1
     tags: []
     deprecation_message: ''
@@ -41,7 +43,8 @@ items:
       A hybrid model which follows the `Inverse` model when close to
       `Class.Sound.RollOffMinDistance` and the `LinearSquare` model when close
       to `Class.Sound.RollOffMaxDistance`.
-      This is done through `Libraries.math.min`((`Class.Sound.RollOffMinDistance`/`Distance`)*`LinearSquare`)
+      This is done through `Libraries.math.min`((`Class.Sound.RollOffMinDistance`/`distance`)*`LinearSquare`),
+      where `distance` is the `Datatype.Vector3.Magnitude` between the audio source and the audio listener.
     value: 3
     tags: []
     deprecation_message: ''