correct ttyd arm binaray

[panpan0000]

https://github.com/kubevela/cloudshell/blob/main/install-ttyd.sh#L12
it use ttyd.arm
I believe it's not for arm server 64bit

my test result:

# my machine is Huawei Tanshan, ARMV8 64bit
[root@arm-taishanv1 ~]# arch
aarch64

[root@arm-taishanv1 ~]# ./ttyd.arm
-bash: ./ttyd.arm: 无法执行二进制文件


[root@arm-taishanv1 ~]#./ttyd.aarch64
ttyd is a tool for sharing terminal over the web

USAGE:
    ttyd [options] <command> [<arguments...>]

VERSION:
    1.6.3-3b174da
......

[panpan0000]

By the way, thank you for your help and I've update my PR in cloudtty/cloudtty#106