Fix test_unsupported_tls_versions with HTTPX (#191)

(cherry picked from commit fa9b474)

Author: pquentin

setup.py

@@ -66,6 +66,8 @@
             "requests",
             "aiohttp",
             "httpx",
+            # https://github.com/encode/httpx/discussions/3214#discussioncomment-10830925
+            "httpcore<1.0.6",
             "respx",
             "opentelemetry-api",
             "opentelemetry-sdk",