correct ttyd arm binaray

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] []

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

```

Start with install-ttyd.sh at line 12 and compare the ttyd.arm binary selected there with the ttyd.aarch64 binary from the report. Test the installer on an ARMV8 aarch64 machine and confirm that the selected binary executes and displays the ttyd usage output.

Written by the indexing model from the issue text.