Minor: Add 2.38.0 section to CHANGES.md (#16804)
Minor: Add 2.38.0 section to CHANGES.md (#16804)


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