cli: do not show install script on Windows client

While running `coder` on the Windows client. I get
```
PS C:\Users\matif> ssh coder.aihwkit
version mismatch: client v0.8.15+9e9a9e0, server v0.9.1+27c8345
download the server version with: 'curl -L https://coder.com/install.sh | sh -s -- --version 0.9.1'
```
The installation script does not work on windows, so this message should not be shown.