build(java): switch to release-please for release tagging (#340)

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Author: yoshi-automation

.github/release-please.yml

@@ -1,2 +1,3 @@
+bumpMinorPreMajor: true
+handleGHRelease: true
 releaseType: java-yoshi
-bumpMinorPreMajor: true

synth.metadata

@@ -4,7 +4,7 @@
  "git": {
  "name": ".",
  "remote": "https://github.com/googleapis/java-aiplatform.git",
- "sha": "591c274ff3ffca5e0d964148eaeebaca5551ecaa"
+ "sha": "eb08618ff647f19824ab2a1266f71b1671f4d0cb"
  }
  },
  {