doc: remove trailing spaces
doc: remove trailing spaces

mroonga/mroonga,yoku0825/mroonga,mroonga/mroonga,naoa/mroonga,naoa/mroonga,yoku0825/mroonga,yoku0825/mroonga,yoku0825/mroonga,naoa/mroonga,mroonga/mroonga,yoku0825/mroonga,naoa/mroonga,naoa/mroonga,naoa/mroonga,mroonga/mroonga,yoku0825/mroonga