howto-install-raspios64: Add section: Update the Bootloader of the Raspberry Pi

[gmacario]

Signed-off-by: Gianpaolo Macario gmacario@gmail.com

Closes #

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• [x] My pull request adheres to the code style of this project
• [ ] My code requires changes to the documentation
• [x] I have updated the documentation as required
• [x] All the tests have passed

ℹ Additional Information

[gmacario]

No negative feedbacks received so far, merging PR on time for dev-cw17 release window.