Update camera.py

[amerob]

• Single Frame Processing: Instead of reading two frames per loop iteration, use one frame and handle frame differencing more efficiently.
• Eliminate Redundant Operations: Like calling cv2.findContours and applying thresholding multiple times, by combining or reusing computations.
• Graceful Exit: Ensure proper handling of user input ('q' key).
• Resource Management: release resources like the webcam and video writer, even if the program is interrupted.
• Improved Code Flow: for better clarity and readability