Update jetpack librealsense installation instructions to reflect the way currently used in ergocub robots

[traversaro]

In https://github.com/icub-tech-iit/documentation/blob/98ca2cb07e0d9bc07990d438e15a73b328736e61/docs/icub_operating_systems/icubos/install-librealsense.md?plain=1 we document that the librealsense is installed from source, but on real robot the situation depends on case by case:

• ergoCubSN002: installed by source, but there the installation process is different as JetPack 6 is used (docs for that are tracked in https://github.com/icub-tech-iit/documentation/blob/98ca2cb07e0d9bc07990d438e15a73b328736e61/docs/icub_operating_systems/icubos/install-librealsense.md?plain=1)
• ergoCubSN001: librealsense is installed from intel official deb packages repo, see https://github.com/IntelRealSense/librealsense/blob/master/doc/installation_jetson.md#4-install-with-debian-packages
• ergoCubSN000: I need to check, I will report this.

[traversaro]

fyi @martinaxgloria @Nicogene

[traversaro]

ergoCubSN000: I need to check, I will report this.

Also there realsense is installed in https://github.com/IntelRealSense/librealsense/blob/master/doc/installation_jetson.md#4-install-with-debian-packages, so at least for JetPack 5 boards, I think it is safe to start documenting that librealsense should be installed via https://github.com/IntelRealSense/librealsense/blob/master/doc/installation_jetson.md#4-install-with-debian-packages .