Hi T45, You have 3 options:
1. Do nothing and stick some black electrical tape over the light (not good)
2. Visit a ECU Tuner who has Woolich software and uncheck the FI O2 sensor and Servo. How does the bike run ? Weak?
Just disconnecting the O2 sensor alone puts it into limp home mode, so surely more was done by the previous Owner.
3. Ebay search for plug in eliminators to fool the ECU that they are still there.
4. IF you got the servo mechanism, reconnect the wiring harness, BUT as far as I know the 750 (and I have a 2019 750) does not have any servo at all. Only the 1000 has it.