Auto merge of #5097 - matklad:end-of-tls-saga-hopefully, r=alexcrichton

Auto merge of #5097 - matklad:end-of-tls-saga-hopefully, r=alexcrichton

Revert "Warn Windows 7 users about old TLS"

We now have upgraded libgit2 version, so Cargo would use TLS 1.2
on windows unconditionally. Note that even *unpatched* windows 7
supports TLS 1.2.

@retep998, you've originally written that

>TLS 1.2 support for Windows 7 still requires a rather recent patch and so even if we do fix that, we should still keep this error message because some people use Windows 7 with automatic updates disabled.

However, it looks like Windows 7 **does** support TLS 1.2 out of the box, and the update is required to enable the use of TLS 1.2 by default:

https://github.com/libgit2/libgit2/issues/4546#issuecomment-368909158

My own testing on a random win 7 virtual box confirms this.

closes https://github.com/rust-lang/cargo/issues/5066