Take the include include-what-you-use asks for

The failure paths added here report through OTEL_INTERNAL_LOG_ERROR with a streamed curl_multi_strerror, which needs ostream. All three iwyu presets ask for it.

Signed-off-by: thc1006 <84045975+thc1006@users.noreply.github.com>

Author: thc1006

ext/src/http/client/curl/http_client_curl.cc

@@ -11,6 +11,7 @@
 #include <functional>
 #include <list>
 #include <mutex>
+#include <ostream>
 #include <string>
 #include <thread>
 #include <unordered_map>