docs: remove reference to sync.Locker (#66)

README.md

@@ -4,7 +4,7 @@
 [![License](https://img.shields.io/badge/license-BSD_3--Clause-brightgreen.svg?style=flat)](https://github.com/gofrs/flock/blob/master/LICENSE)
 [![Go Report Card](https://goreportcard.com/badge/github.com/gofrs/flock)](https://goreportcard.com/report/github.com/gofrs/flock)
 
-`flock` implements a thread-safe `sync.Locker` interface for file locking.
+`flock` implements a thread-safe file lock.
 
 It also includes a non-blocking `TryLock()` function to allow locking without blocking execution.