binman: don't import deprecated distutils package

'make tests' fails on Ubuntu 22.04 with:

binman: ./tools/binman/binman:12: DeprecationWarning:
The distutils package is deprecated and slated for removal in Python 3.12.
Use setuptools or check PEP 632 for potential alternatives
  from distutils.sysconfig import get_python_lib
./tools/binman/binman:12: DeprecationWarning:
The distutils.sysconfig module is deprecated, use sysconfig instead
  from distutils.sysconfig import get_python_lib
<unittest.result.TestResult run=428 errors=0 failures=4>
AssertionError: 0 != 468

As we don't use Ubuntu 16.04 for our CI anymore drop the import.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>