build: remove codecov action (#451)

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Source-Link: googleapis/synthtool@b891fb4

packages/google-cloud-dns/synth.metadata

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/nodejs-dns.git",
-        "sha": "eb4614ba61f3d70e83be23e9296db80a3a684558"
+        "sha": "f3db0931622f2f7c9e177d533a5337baa4386284"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "e6f3d54be015a394b6ab5a25903ec09062a2b424"
+        "sha": "b891fb474173f810051a7fdb0d66915e0a9bc82f"
       }
     }
   ]