Well that's two hours of my life I won't get back. Had to pull out two sensors, the one I broke, and the replacement off another plenum. Both were extremely difficult.
I brute forced the first one by luck after a very long time of trying. The second one is the method I want to share:
Get the rectangle clip off, that's easy. Now it'll still be stuck. Looking at the sensor from inside the plenum you'll notice that if you rotate it 45 degrees in either direction the prongs of the sensor retract. That's because the hole is actually cross (+) shaped and when you rotate it the inner corners of the cross are pressing against the prongs and retracting them. This might lead you to believe that you then pull it once the prongs are retracted, but that is not going to work; the prongs have to come out aligned with the cross.
So, rotate the sensor back and forth 45* in both directions to exercise the prongs a few or however many times it feels right. Then rotate 45 to retract, then apply pulling pressure on the connector side of the sensor while rotating back to zero. Hopefully that prong that you're pulling on will stay retracted at zero and is starting to move out. Keep the pulling pressure on the connector side. On the opposite side of the sensor, use a flathead screwdriver to gently apply pressure to the tab/lip there, and pry the sensor out slowly. Pry too hard and you break the tab off the sensor, which happened to me.
There you go. Good luck. I have no idea why it has to be designed this way. A two second job turned into hours. I hope never to have to try this again.