nit: update doxygen comments

Signed-off-by: jncfa <[email protected]>

Author: jncfa

rosbag2_cpp/include/rosbag2_cpp/cache/circular_message_cache.hpp

@@ -58,8 +58,7 @@ class ROSBAG2_CPP_PUBLIC CircularMessageCache
 
   /// Puts msg into circular buffer, replacing the oldest msg when buffer is full
   /// \return True if message was successfully pushed, otherwise false.
-  /// NOTE: This will always return true, since the circular buffer by design drops old messages
-  /// when the buffer is full.
+  /// NOTE: This will always return true, unless message is null or too large for the buffer.
   bool push(std::shared_ptr<const rosbag2_storage::SerializedBagMessage> msg) override;
 
   /// Get current buffer to consume.