[PC-1452/1454/1455] Portenta X8 User Manual: Flashing Mode Section Update (incl. Portenta Hat Carrier) (#1482)

* X8 user manual flashing section update

* User manual content update

* User manual ssh content update

* User manual ssh content update

* User manual content update

* User manual content update patch

* Update content/hardware/04.pro/boards/portenta-x8/tutorials/01.user-manual/content.md

Co-authored-by: Julián Caro Linares <jcarolinares@gmail.com>

* Update content/hardware/04.pro/boards/portenta-x8/tutorials/01.user-manual/content.md

Co-authored-by: Julián Caro Linares <jcarolinares@gmail.com>

* User manual ssh content post update

* User manual ssh content post update

* User manual ssh content minor update

* Apply suggestions from code review

Marta's feedback added

Co-authored-by: martab1994 <93210545+martab1994@users.noreply.github.com>

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Co-authored-by: TaddyHC <k.hochung@arduino.cc>
Co-authored-by: TaddyHC <94547080+TaddyHC@users.noreply.github.com>
Co-authored-by: Julián Caro Linares <jcarolinares@gmail.com>
Co-authored-by: martab1994 <93210545+martab1994@users.noreply.github.com>

Author: 4 people