Revert "build-mono-package: create "virtual" version 3.0.6.1, with locker's patch"

This reverts commit 3ad42fa5778771bd3a9eb7da3f5079177e6c73fc,
because I think this "virtual version" is not needed anymore
(just grab any of the Mono's 3.2.x tags*, which should include
the patch that this version included:

https://github.com/mono/mono/commit/ada85c64adcbd260c7e5ee284c628d0f41ad4ca6

Or 3.0.12 tag, which is the last 3.0.x tag to include this,
which doesn't default to SGEN garbage collector.)