[BEAM-12558] Fix doc typo.
[BEAM-12558] Fix doc typo.

lukecwik/incubator-beam,apache/beam,apache/beam,robertwb/incubator-beam,lukecwik/incubator-beam,lukecwik/incubator-beam,lukecwik/incubator-beam,chamikaramj/beam,chamikaramj/beam,chamikaramj/beam,apache/beam,chamikaramj/beam,apache/beam,robertwb/incubator-beam,chamikaramj/beam,lukecwik/incubator-beam,chamikaramj/beam,apache/beam,chamikaramj/beam,lukecwik/incubator-beam,robertwb/incubator-beam,robertwb/incubator-beam,apache/beam,robertwb/incubator-beam,apache/beam,apache/beam,chamikaramj/beam,lukecwik/incubator-beam,apache/beam,robertwb/incubator-beam,lukecwik/incubator-beam,lukecwik/incubator-beam,chamikaramj/beam,robertwb/incubator-beam,chamikaramj/beam,lukecwik/incubator-beam,apache/beam,robertwb/incubator-beam,robertwb/incubator-beam,robertwb/incubator-beam,apache/beam