Update USB_FLASH_DRIVE_SUPPORT (#15021)

Marlin/src/sd/usb_flashdrive/lib-uhs2/README.txt

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+
+==== USB HOST SHIELD 2.0 LIBRARY ====
+
+The lib/ folder contains a subset of the files from the USB Host Shield 2.0
+library:
+
+  https://github.com/felis/USB_Host_Shield_2.0
+
+While the original library was released under the GPLv2 and could not be
+commingled with Marlin, the developers have graciously re-licenced the
+files needed for Marlin as "GPLv2 or later", as documented in this thread.
+
+  https://github.com/felis/USB_Host_Shield_2.0/issues/364
+
+Small modifications have been made to the source. Please search for
+USB_FLASH_DRIVE_SUPPORT or look at the patch file to see what was changed.
+
+==== LICENSE SUMMARY ====
+
+Source Path:                 Repository:                           License:
+------------                 -----------                           --------
+lib-uhs3/                    github.com/felis/USB_Host_Shield_2.0  GPLv2 or later
+lib-uhs3/lib/masstorage.cpp  github.com/greiman/UsbFat [1]         MIT
+lib-uhs3/lib/settings.h      github.com/greiman/UsbFat [1]         MIT
+
+[1] Changes related to SKIP_WRITE_PROTECT and DELAY only
+
+==== PERFORMANCE ENHANCEMENTS FOR USB DRIVES ====
+
+There are also some small performance enhancements from Bill Greiman, regarding
+SKIP_WRITE_PROTECT and DELAY. These changes came from the following repo:
+
+   https://github.com/greiman/UsbFat
+
+While the original library was released under the GPLv2 and could not be
+commingled with Marlin, the developer has graciously re-licenced his changes
+under the "MIT" license, as documented here:
+
+   https://github.com/greiman/UsbFat/issues/8
+
+==== MARLIN INTEGRATION WORK ====
+
+All additional work done to integrate USB into Marlin was performed by AlephObjects, Inc.
+and is licensed under the GPLv3.
+
+-- marcio@alephobjects.com