bump curl-sh exprs to tls 1.3?

We currently emit curl-sh exprs of the form:

```
curl --proto '=https' --tlsv1.2 -LsSf https://github.com/axodotdev/cargo-dist/releases/download/v0.3.0/cargo-dist-installer.sh | sh
```

This was inherited from https://rustup.rs/ although we added the extra `-L` (iirc required to chase redirects from github).

It has been suggested we should update this to tlsv1.3 -- I'm not really a tls/interop expert, so feedback welcome.

Locate the code that emits the curl-sh expression shown in the issue, then compare its TLS behavior with rustup.rs and curl's documented --tlsv1.3 support. Resolve the interoperability question before changing the generated command, and verify that the emitted installer command uses the agreed TLS version.

Written by the indexing model from the issue text.