Well, that's a bit tricky, and subject to some interpretation.
In Canada, the closest I can find to this would be in the list of tasks a pilot may carry out (does not require a maintenance person):
(27) deactivating or securing inoperative systems in accordance with sections
605.09 or
605.10 of the CARs, including the installation of devices specifically intended for system deactivation, where the work does not involve disassembly, the installation of parts, or testing other than operational checks;
Cessnas of this type did not leave the factory with circuit breakers you could pull. The earlier Cessnas had fuses, but often the circuits were joined, so that you'd loose several systems by removing one fuse.
So, personally, I would be comfortable removing the cannon plug from the back of the turn co-ordinator, TYING IT PROPERLY OUT OF THE WAY, AND CONFIRMING THAT NOTHING IS FOULING BACK THERE! then marking the face of the instrument "inoperative" and flying within the suitably appropriate day VFR limits for the aircraft and pilot skill.
That said, that's me. You have to do only what YOU are comfortable with, and within FAA regs, not Canada's. It is possible that you could be asked to justify what you had done - satisfy yourself you could!