setup.py: drop data_files, installs LICENSE to incorrect place

As reported in issue
xmlrunner#284, the
data_files statement in the setup() calls installs the LICENSE file in
the wrong place: in /usr/LICENSE, or even /LICENSE depending on the
configuration.

So let's drop this, and let setuptools install the LICENSE file
automatically: since setuptools v56, the license_files attribute is
automatically assigned to a default value, which includes "LICENSE",
so there is in fact nothing to do to the get the LICENSE file
installed at the correct location. See
https://setuptools.pypa.io/en/latest/history.html#v56-0-0.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

Author: tpetazzoni

setup.py

@@ -27,7 +27,6 @@
     description = 'unittest-based test runner with Ant/JUnit like XML reporting.',
     long_description = long_description,
     long_description_content_type = 'text/markdown',
-    data_files = [('', ['LICENSE'])],
     install_requires = ['lxml'],
     license = 'BSD',
     platforms = ['Any'],