set tls v1.2 for powershell installers as well

[Gankra]

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

Unfortunately I think this affects the initial irm call.

I think we want the -SslProtocol flag?

[Gankra]

per the linked issue, a bit messier than i'd like (the obvious flags are too new for the platforms where this matters)

[Gankra]

the user did find this works

[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12;
irm https://astral.sh/uv/install.ps1 | iex

but lord that makes me sad to ask someone to run

[Gankra]

5.1 is the last version of powershell windows users have (everything after is "core")

https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/invoke-restmethod?view=powershell-5.1

[Gankra]

Presumably they got this from https://blog.pauby.com/post/force-powershell-to-use-tls-1-2/ (i've seen it in azure docs too tho)