Using default SSLContext for HTTPS requests in an HTTPS proxy doesn't verify certificate hostname for proxy connection

Impact Users who are using an HTTPS proxy to issue HTTPS requests and haven't configured their own SSLContext via proxyconfig. Only the default SSLContext is impacted. Patches urllib3 =1.26.4 has the issue resolved. urllib31.26 is not impacted due to not supporting HTTPS requests via HTTPS proxie...