streaming: remove unused operator==

since this operator is used nowhere, let's drop it.

Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>

Closes #13697

streaming/stream_manager.hh

@@ -54,7 +54,6 @@ struct stream_bytes {
         ret += y;
         return ret;
     }
-    friend bool operator==(const stream_bytes&, const stream_bytes&) = default;
     stream_bytes& operator+=(const stream_bytes& x) {
         bytes_sent += x.bytes_sent;
         bytes_received += x.bytes_received;