set tls v1.2 for powershell installers as well

see: https://github.com/astral-sh/uv/issues/2085

Unfortunately I think this affects the initial `irm` call.

I think we want the [-SslProtocol](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/invoke-restmethod?view=powershell-7.4#-sslprotocol) flag?

Start by tracing how cargo-dist generates and invokes its PowerShell installer, paying particular attention to the initial `irm` call mentioned in the issue. Check the documented `-SslProtocol` behavior and confirm that the installer uses TLS 1.2 for that request; done means the generated PowerShell installer works with the affected environments.

Written by the indexing model from the issue text.