build: --credential-file-override is no longer required (#418)

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Source-Link: googleapis/synthtool@94421c4

packages/google-cloud-dns/synth.metadata

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/nodejs-dns.git",
-        "sha": "329295fc8bedef5fff1b13112d311405a90189c1"
+        "sha": "f96c2ad5078eb0294a1ea75fec48252de743087e"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "5936421202fb53ed4641bcb824017dd393a3dbcc"
+        "sha": "94421c47802f56a44c320257b2b4c190dc7d6b68"
       }
     }
   ]