typo : FW_RR -> FW_PR

[Param Deshpande]

There's a typo in manual tuning for FW. For pitch tuning, mentions roll parameters to be minimum instead.
Corrections - > FW_RR* should be made FW_PR* minimum in pitch section.

[Hamish Willee]

Would you like to PR in a change?

[Hamish Willee]

Thanks. Fixed by #2962