build: rename _toc to toc (#413)

This PR was generated using Autosynth. 🌈

Synth log will be available here:
https://source.cloud.google.com/results/invocations/940354f9-15cd-4361-bbf4-dc9af1426979/targets

- [ ] To automatically regenerate this PR, check this box.

Source-Link: googleapis/synthtool@99c93fe

packages/google-cloud-dns/synth.metadata

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/nodejs-dns.git",
-        "sha": "06c3a3caefaf98dcc7875a979fea27895cf2a1e1"
+        "sha": "1c36ba649d537649c4bb6f14ab2b434539b85473"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "21f1470ecd01424dc91c70f1a7c798e4e87d1eec"
+        "sha": "99c93fe09f8c1dca09dfc0301c8668e3a70dd796"
       }
     }
   ]