python-dtfabric-20220219-bp156.2.1

- rm explict BuildRequires python38 to allow this to build on older releases of openSUSE

-update to 20220219
  * No changelog was provided.
-update source to refer to github which is where dtfabric is developed
-remove tests-improved.patch
  * incorporated into upstream, no longer needed/applies

- Add tests-improved.patch gh#libyal/dtfabric#25

- Update to 20200621 release
  * No changelog was provided.

- Setup use of update-alternatives for the package binary.

- Initial effort to package dtfabric 20190120