package/brltty: bump to version 6.5
README hash changed due to version update:
https://github.com/brltty/brltty/commit/4bb7f50767b8b99ea75aebda82c84b8e0df167b3
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>