Tweak BLOCK_BUFFER_SIZE description

Marlin/Configuration_adv.h

Marlin/src/config/default/Configuration_adv.h

...src/config/examples/AlephObjects/TAZ4/Configuration_adv.h

Marlin/src/config/examples/Anet/A6/Configuration_adv.h

Marlin/src/config/examples/Anet/A8/Configuration_adv.h

Marlin/src/config/examples/Azteeg/X5GT/Configuration_adv.h

Marlin/src/config/examples/BQ/Hephestos/Configuration_adv.h

...in/src/config/examples/BQ/Hephestos_2/Configuration_adv.h

Marlin/src/config/examples/BQ/WITBOX/Configuration_adv.h

Marlin/src/config/examples/Cartesio/Configuration_adv.h

...in/src/config/examples/Creality/CR-10/Configuration_adv.h

Marlin/src/config/examples/Felix/Configuration_adv.h

...rc/config/examples/FolgerTech/i3-2020/Configuration_adv.h

.../src/config/examples/Infitary/i3-M508/Configuration_adv.h

Marlin/src/config/examples/Malyan/M150/Configuration_adv.h

...config/examples/Micromake/C1/enhanced/Configuration_adv.h

Marlin/src/config/examples/Mks/Sbase/Configuration_adv.h

Marlin/src/config/examples/RigidBot/Configuration_adv.h

Marlin/src/config/examples/SCARA/Configuration_adv.h

Marlin/src/config/examples/Sanguinololu/Configuration_adv.h