Panda loads the display modules that have been specified in the Config.prc file (through load-display and aux-display lines) and lists which ones are available for rendering. Examples are the "pandagl" module, which makes the "wglGraphicsPipe" rendering pipeline available on Windows (the OpenGL renderer), and the "pandadx8" and "pandadx9" modules (with the respective DirectX renderers).
If you really wish to hide this information, you can start Panda with "window-type none" to prevent it from creating the window, creating the pipe and opening the window explicitly, telling Panda not to output the pipe types when opening the pipe:
However, there is no real reason to suppress it, as it won't appear in a deployed game (only in the log file). You can also redirect this output to a log file yourself if you wish, by setting the "notify-out" configuration variable to a filename in your Config.prc file.