fix: use rustls as curl backend to avoid CI failure.

Note that doing so might be less compatible due to `ring`, which
is why it's not the default.
There may also be other side-effects, like which certificate store
is used, so let's not enforce this.

justfile

@@ -191,7 +191,7 @@ jtt := target_dir / "debug/jtt"
 
 # run journey tests (max)
 journey-tests:
-    cargo build
+    cargo build --features http-client-curl-rustls
     cargo build -p gix-testtools --bin jtt
     ./tests/journey.sh {{ ein }} {{ gix }} {{ jtt }} max