Fix alluxio-fuse umount help message

[secfree]

What changes are proposed in this pull request?

Fix alluxio-fuse umount help message

Why are the changes needed?

The current help message is misguiding. Please check the below case

$ ./dora/integration/fuse/bin/alluxio-fuse umount mnt
...
Terminating 3315520..........................................................
[2024-02-02T10:33:28+0800]: Failed to kill fuse process [3315520] after 60 seconds.
Run "alluxio-fuse umount -f mount_point" if needed to forcibly kill the alluxio fuse process and fuse mount point.

$ ./dora/integration/fuse/bin/alluxio-fuse umount -f mnt
basename: invalid option -- 'f'
Try 'basename --help' for more information.

putting "-f" after the mount_point parameter is ok

$ ./dora/integration/fuse/bin/alluxio-fuse umount mnt -f
Forcibly killed fuse process 3315520

Does this PR introduce any user facing changes?

NO