DOC: fixed two more typos in docstrings
DOC: fixed two more typos in docstrings

nanpercentile and nanquantile had the same typo I just fixed in percentile
endolith/numpy,mattip/numpy,mhvk/numpy,mattip/numpy,mhvk/numpy,charris/numpy,endolith/numpy,mhvk/numpy,mhvk/numpy,mattip/numpy,mhvk/numpy,mattip/numpy,numpy/numpy,numpy/numpy,numpy/numpy,endolith/numpy,charris/numpy,charris/numpy,charris/numpy,endolith/numpy,numpy/numpy