build: --credential-file-override is no longer required (#665)

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Source-Link: googleapis/synthtool@94421c4

packages/google-cloud-dialogflow/synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/nodejs-dialogflow.git",
-        "sha": "416acb5d3e216b243c02ea9c20f51f1a83e7e977"
+        "sha": "68120ab07ad02d8f6e6a54a471b6d8ee3c124d56"
       }
     },
     {
@@ -19,7 +19,7 @@
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "89d431fb2975fc4e0ed24995a6e6dfc8ff4c24fa"
+        "sha": "94421c47802f56a44c320257b2b4c190dc7d6b68"
       }
     }
   ],