package/brltty: bump version to 6.1

package/brltty: bump version to 6.1

Changelog: https://brltty.app/doc/ChangeLog.txt

Removed patches committed upstream:
https://github.com/brltty/brltty/commit/0414ad2b4e8978a14343d920a5a1f11da892eaf3
https://github.com/brltty/brltty/commit/a2e3aa25e8ef5044422aeeaa65968f97550b5e8d

Updated hash of README due to non-license related commits:
https://github.com/brltty/brltty/commits/master/README

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>