fix(build): migrate to using main branch

.github/.OwlBot.lock.yaml

@@ -1,3 +1,3 @@
 docker:
   image: gcr.io/repo-automation-bots/owlbot-nodejs:latest
-  digest: sha256:6245a5be4c0406d9b2f04f380d8b88ffe4655df3cdbb57626f8913e8d620f4dd
+  digest: sha256:72ff93409133b0cf277b8870f859e1ddde62d2e329f655311d4bfc16735d182e

.github/generated-files-bot.yml

@@ -8,9 +8,9 @@ generatedFiles:
 - path: '.github/generated-files-bot.+(yml|yaml)'
   message: '`.github/generated-files-bot.(yml|yaml)` should be updated in [`synthtool`](https://github.com/googleapis/synthtool)'
 - path: 'README.md'
-  message: '`README.md` is managed by [`synthtool`](https://github.com/googleapis/synthtool). However, a partials file can be used to update the README, e.g.: https://github.com/googleapis/nodejs-storage/blob/master/.readme-partials.yaml'
+  message: '`README.md` is managed by [`synthtool`](https://github.com/googleapis/synthtool). However, a partials file can be used to update the README, e.g.: https://github.com/googleapis/nodejs-storage/blob/main/.readme-partials.yaml'
 - path: 'samples/README.md'
-  message: '`samples/README.md` is managed by [`synthtool`](https://github.com/googleapis/synthtool). However, a partials file can be used to update the README, e.g.: https://github.com/googleapis/nodejs-storage/blob/master/.readme-partials.yaml'
+  message: '`samples/README.md` is managed by [`synthtool`](https://github.com/googleapis/synthtool). However, a partials file can be used to update the README, e.g.: https://github.com/googleapis/nodejs-storage/blob/main/.readme-partials.yaml'
 ignoreAuthors:
 - 'gcf-owl-bot[bot]'
 - 'yoshi-automation'

README.md

@@ -6,7 +6,7 @@
 
 [![release level](https://img.shields.io/badge/release%20level-beta-yellow.svg?style=flat)](https://cloud.google.com/terms/launch-stages)
 [![npm version](https://img.shields.io/npm/v/@google-cloud/documentai.svg)](https://www.npmjs.org/package/@google-cloud/documentai)
-[![codecov](https://img.shields.io/codecov/c/github/googleapis/nodejs-document-ai/master.svg?style=flat)](https://codecov.io/gh/googleapis/nodejs-document-ai)
+[![codecov](https://img.shields.io/codecov/c/github/googleapis/nodejs-document-ai/main.svg?style=flat)](https://codecov.io/gh/googleapis/nodejs-document-ai)
 
 
 
@@ -197,8 +197,8 @@ Contributions welcome! See the [Contributing Guide](https://github.com/googleapi
 Please note that this `README.md`, the `samples/README.md`,
 and a variety of configuration files in this repository (including `.nycrc` and `tsconfig.json`)
 are generated from a central template. To edit one of these files, make an edit
-to its template in this
-[directory](https://github.com/googleapis/synthtool/tree/master/synthtool/gcp/templates/node_library).
+to its templates in
+[directory](https://github.com/googleapis/synthtool).
 
 ## License