Migrate references from master to main (#23)

Author: rogebrd

.github/workflows/dispatch_spec_update.yml

@@ -3,7 +3,7 @@ on:
   workflow_dispatch:
   push:
     branches:
-      - master
+      - main
 
 jobs:
   Dispatch:

README.md

@@ -27,6 +27,6 @@ The API Spec is distributed under the MIT license, please see [LICENSE][license]
 
 [logo]: https://cfl.dropboxstatic.com/static/images/sdk/api_spec_banner.png
 [repo]: https://github.com/dropbox/dropbox-api-spec
-[license]: https://github.com/dropbox/dropbox-api-spec/blobs/master/LICENSE
-[contributing]: https://github.com/dropbox/dropbox-api-spec/blobs/master/CONTRIBUTING.md
+[license]: https://github.com/dropbox/dropbox-api-spec/blobs/main/LICENSE
+[contributing]: https://github.com/dropbox/dropbox-api-spec/blobs/main/CONTRIBUTING.md
 [support]: https://www.dropbox.com/developers/contact