fix: remove invalid 'done' keyword from PowerShell tunnel script

[Nepomuk5665]

Summary

Removes an invalid done keyword from the PowerShell script generated by windows_tunnel_cmd in lib/taste_tester/tunnel.rb.

The Bug

The windows_tunnel_cmd method generates a PowerShell heredoc for creating SSH tunnels on Windows targets. However, the script incorrectly includes a done keyword at the end of the while loop:

while ($true) {
    # ... loop body ...
    sleep 60
}
done  # <-- Invalid PowerShell syntax

Why This Is Wrong

• done is bash/shell syntax used to close while, for, and until loops
• PowerShell uses braces {} to delimit code blocks, not keywords
• A PowerShell while loop is simply while (condition) { body } - no closing keyword needed
• The done line causes a syntax error when Windows attempts to run the tunnel script

Impact

This bug prevents SSH tunnel creation on Windows targets. When taste-tester attempts to set up a tunnel to a Windows host, PowerShell will reject the script with a syntax error, causing the tunnel setup to fail.

Fix

Simply remove the stray done line. The while loop is already properly closed by its closing brace }.