Get rid off "master" word in the project

Author: artembilan

README.md

@@ -648,7 +648,7 @@ The `com.amazonaws:dynamodb-lock-client` dependency must be present to make a `D
 [https://aws.amazon.com/documentation/ses/]: https://aws.amazon.com/documentation/ses/
 [FTP/FTPS Adapters Chapter]: https://docs.spring.io/spring-integration/reference/html/ftp.html
 [Pull requests]: https://help.github.com/en/articles/creating-a-pull-request
-[contributor guidelines]: https://github.com/spring-projects/spring-integration/blob/master/CONTRIBUTING.adoc
+[contributor guidelines]: https://github.com/spring-projects/spring-integration/blob/main/CONTRIBUTING.adoc
 [administrator guidelines]: https://github.com/spring-projects/spring-integration/wiki/Administrator-Guidelines
 [Dynalite]: https://github.com/mhart/dynalite
 [DynamoDB TTL]: https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/TTL.html