package/synergy: bump version to 2.0.12-beta

package/synergy: bump version to 2.0.12-beta

Normally we do not use beta versions but 1.x versions are incompatible
with openssl-1.1.x and openssl support was dropped in synergy with
version 2.0.4: https://github.com/symless/synergy-core/releases

Also libcurl is not needed anymore since version 2.0.12.

Added license hash, removed all patches since they fixed bugs which do
not exist anymore.

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