ci: remove the separate rustls backend regression step

Keep the HTTPS discovery regression in the existing test archive and
runner. Avoid an extra core test build solely to enable both rustls
backends; that combination was verified locally before the TLS fix.

.github/workflows/test.yml

@@ -125,13 +125,6 @@ jobs:
 
       - uses: taiki-e/install-action@nextest
 
-      - name: Test HTTPS discovery with both rustls backends
-        # Catch provider-selection panics even when release features use only ring.
-        run: >-
-          cargo test --locked --package easytier-core --lib
-          --features rustls/aws_lc_rs
-          https_fetch_reaches_tls_handshake_without_global_provider
-
       - name: Archive test
         run: >-
           cargo nextest archive --archive-file tests.tar.zst