refactor(nodejs): move build cop to flakybot (#356)

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Source-Link: googleapis/synthtool@57c23fa

packages/google-cloud-securitycenter/synth.metadata

@@ -4,7 +4,7 @@
  "git": {
  "name": ".",
  "remote": "https://github.com/googleapis/nodejs-security-center.git",
- "sha": "6c3455c447cfc9772213833af1543edb58d8ba92"
+ "sha": "fb74f8aea857c140f9c680fe800f9d244f31ac21"
  }
  },
  {
@@ -19,7 +19,7 @@
  "git": {
  "name": "synthtool",
  "remote": "https://github.com/googleapis/synthtool.git",
- "sha": "363fe305e9ce34a6cd53951c6ee5f997094b54ee"
+ "sha": "57c23fa5705499a4181095ced81f0ee0933b64f6"
  }
  }
  ],