chore: enable release-trigger bot (#176)

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

.github/release-trigger.yml

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

synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-workflow-executions.git",
-        "sha": "4f2b2daed48cc6e6d0305468e611b91c6b101be8"
+        "sha": "80b4245bdb48e42a41c8d1263acc7ff54517a55d"
       }
     },
     {
@@ -27,7 +27,7 @@
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "ff01716e16d2c6e87eaf87197b753ac9fcbbed5d"
+        "sha": "63cff634aabb85854caa511c5837ea6b45f42b4b"
       }
     }
   ],
@@ -61,6 +61,7 @@
     ".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",