chore: enable release-trigger bot (#533)

This PR was generated using Autosynth. 🌈 Synth log will be available here: https://source.cloud.google.com/results/invocations/92fa7cae-d50e-4e3e-8dea-e6388563196c/targets - [ ] To automatically regenerate this PR, check this box. (May take up to 24 hours.) Source-Link: googleapis/synthtool@63cff63

Author: yoshi-automation

.github/release-trigger.yml

@@ -0,0 +1 @@
+enabled: true

synth.metadata

@@ -4,7 +4,7 @@
  "git": {
  "name": ".",
  "remote": "https://github.com/googleapis/java-websecurityscanner.git",
- "sha": "f712f4b522e7a0aee9e75c1d7803f9c9911cb237"
+ "sha": "126daca700fc139d2c62b3ebac01704194f9b32d"
  }
  },
  {
@@ -35,7 +35,7 @@
  "git": {
  "name": "synthtool",
  "remote": "https://github.com/googleapis/synthtool.git",
- "sha": "ff01716e16d2c6e87eaf87197b753ac9fcbbed5d"
+ "sha": "63cff634aabb85854caa511c5837ea6b45f42b4b"
  }
  }
  ],
@@ -78,6 +78,7 @@
  ".github/generated-files-bot.yml",
  ".github/readme/synth.py",
  ".github/release-please.yml",
+ ".github/release-trigger.yml",
  ".github/snippet-bot.yml",
  ".github/sync-repo-settings.yaml",
  ".github/trusted-contribution.yml",