upgrade.php: If we're on windows, make sure we can load intermediate certificates

[jerm]

According to curl/curl#12155 and curl/curl@2d63331

Some corporate Windows proxy (mis)configurations don't pass along
intermediate certificates in their TLS handshakes, breaking lots of
things that don't work around it.

This creates a problem in our curl calls when checking for
.upgrade_requirements.json, and seems to be the source of errors for a
few of our users: #14826 (comment)

In this change, we detect when running on windows environments and load
the curl option that works around this. Loading it in non-windows
environments throws an error, hence the check.

[what-the-diff]

PR Summary

• Enhanced SSL Configuration on Windows
  In order to ensure a robust and secure communication, this PR adds a condition that adjusts the SSL options of the CURL (a tool used to transfer data) when the operating system is Windows (identified as "WINNT"). This will allow the software to use the native Certificate Authority bundle from the Windows OS, increasing the level of security for data transfers.