zed: remove unused zed_file_close_on_exec()

The FIXME comment was there since the initial implementation in 2014,
there are no users

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes openzfs#11807

cmd/zed/zed_file.c

@@ -187,31 +187,3 @@ zed_file_close_from(int lowfd)
 
 	errno = errno_bak;
 }
-
-/*
- * Set the CLOEXEC flag on file descriptor [fd] so it will be automatically
- * closed upon successful execution of one of the exec functions.
- * Return 0 on success, or -1 on error.
- *
- * FIXME: No longer needed?
- */
-int
-zed_file_close_on_exec(int fd)
-{
-	int flags;
-
-	if (fd < 0) {
-		errno = EBADF;
-		return (-1);
-	}
-	flags = fcntl(fd, F_GETFD);
-	if (flags == -1)
-		return (-1);
-
-	flags |= FD_CLOEXEC;
-
-	if (fcntl(fd, F_SETFD, flags) == -1)
-		return (-1);
-
-	return (0);
-}

cmd/zed/zed_file.h

@@ -30,6 +30,4 @@ pid_t zed_file_is_locked(int fd);
 
 void zed_file_close_from(int fd);
 
-int zed_file_close_on_exec(int fd);
-
 #endif	/* !ZED_FILE_H */