Why would you want to remove the encoder strip? The strip can be carefully cleaned in place by following the instructions here
If you really want to remove the strip (not recommended) open the lid (with the power on). Wait for the printer noises to stop, then carefully move the carriage (with the print cartridges in it) to the left. Unplug the printer power.
The encoder is held on a metal tang at the right side and a spring on the left side. Carefully grasp the encoder near the right side and pull it to the right so it can be dislodged from the tang on the right. You will need to bend the encoder slightly to unhook the end. Once it has been loosened form the right you can then release the left tang and carefully remove the encoder.
When reinstalling the encoder reverse these steps. First thread it properly through the sensor on the back of the carriage, then connect the left end to the spring, then connect the right side.
Bob Headrick, Microsoft MVP Printing/Imaging