Quick way
Using the local adjustment tools brush, set the Saturation to zero. and using a large area brush paint over the whole area. Make sure you turn off "Auto Mask".
Now depress the alt/ option key, this gives you a "-" sign in the center of the brush. You may want to reduce the size of the brush to suit the area you are working on . Now simply go over the area you want to restore as this removes the "Zero Saturation" you have applied