docs: generate sample code in the Java microgenerator (#25)

This PR was generated using Autosynth. 🌈

Synth log will be available here:
https://source.cloud.google.com/results/invocations/451b25a8-87ff-414f-8c57-e8e27a8ff40f/targets

- [ ] To automatically regenerate this PR, check this box.

PiperOrigin-RevId: 357800868
Source-Link: googleapis/googleapis@e8bc447
PiperOrigin-RevId: 356341083
Source-Link: googleapis/googleapis@8d8c008