Remove 8th exercise on CPP which requires video

Author: banchan86

tutorials/hobgoblin-reaction.md

@@ -269,30 +269,12 @@ stateDiagram-v2
 
 - Record a timestamped chronological log of trial types and rewards into a CSV file using a [`BehaviorSubject`].
 
-### Exercise 8: Conditioned place preference
-
-Implement the following trial structure for conditioned place preference. `enter` and `leave` events should be triggered in real-time from the camera, by tracking an object moving in or out of a region of interest (ROI). `Reward` should be triggered once upon entering the ROI, and not repeat again until the object exits the ROI and the ITI has elapsed.
-
-```mermaid
-stateDiagram-v2
-    direction LR
-    ITI --> Ready: elapsed
-    Ready --> Reward: enter
-    Reward --> ITI: leave
-```
-
-> [!Tip]
-> There are several ways to implement ROI activation, so feel free to explore different ideas. Consider using either [`Crop`], [`RoiActivity`], or [`ContainsPoint`] as part of different strategies to implement the `enter` and `leave` events.
-
 <!--Reference Style Links -->
 [`BehaviorSubject`]: xref:Bonsai.Reactive.BehaviorSubject
 [`BitwiseNot`]: xref:Bonsai.Expressions.BitwiseNotBuilder
 [`Boolean`]: xref:Bonsai.Expressions.BooleanProperty
 [`Condition`]: xref:Bonsai.Reactive.Condition
-[`ContainsPoint`]: xref:Bonsai.Vision.ContainsPoint
 [`CreateMessage`]: xref:Harp.Hobgoblin.CreateMessage
-[`Crop`]: xref:Bonsai.Vision.Crop
-[`RoiActivity`]: xref:Bonsai.Vision.RoiActivity
 [`Delay`]: xref:Bonsai.Reactive.Delay
 [`Device`]: xref:Harp.Hobgoblin.Device
 [`DeviceDataWriter`]: xref:Harp.Hobgoblin.DeviceDataWriter