Update install-kusion.sh for OS X Tahoe base64 change

[yolabingo]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

run scripts/install-kusion.sh on OS X Tahoe

2. What did you expect to see? (Required)

helm install of Kusion server

3. What did you see instead (Required)

base64: invalid option -- 'b'
Try 'base64 --help' for more information.

base64 arguments changed in OS X Tahoe

base64 --help

Usage: base64 [OPTION]... [FILE]
Base64 encode or decode FILE, or standard input, to standard output.

With no FILE, or when FILE is -, read standard input.

Mandatory arguments to long options are mandatory for short options too.
  -d, --decode          decode data
  -i, --ignore-garbage  when decoding, ignore non-alphabet characters
  -w, --wrap=COLS       wrap encoded lines after COLS character (default 76).
                          Use 0 to disable line wrapping
      --help        display this help and exit
      --version     output version information and exit

The data are encoded as described for the base64 alphabet in RFC 4648.
When decoding, the input may contain newlines in addition to the bytes of
the formal base64 alphabet.  Use --ignore-garbage to attempt to recover
from any other non-alphabet bytes in the encoded stream.

GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Full documentation <https://www.gnu.org/software/coreutils/base64>
or available locally via: info '(coreutils) base64 invocation'

4. What is your KusionStack components version? (Required)

n/a