scripts/buildhistory-diff: drop use of distutils

The use of distutils.version.LooseVersion to check for GitPython > 0.3.1
is not really needed anymore since any supported distribution has at least
1.0.0 (centos-7 via epel7, debian-9, ubuntu-16.04)

If we want to reinstate this check, alternatives would be to require
python3-packaging on all hosts and use packaging.version.Version or
use an imported LooseVersion in bb.version.

[YOCTO #14610]

(From OE-Core rev: bc90dcae9f53ddc246942f4d9b8ae8943e3b9754)

Signed-off-by: Tim Orling <timothy.t.orling@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/buildhistory-diff

@@ -11,7 +11,6 @@
 import sys
 import os
 import argparse
-from distutils.version import LooseVersion
 
 # Ensure PythonGit is installed (buildhistory_analysis needs it)
 try:
@@ -73,10 +72,6 @@ def main():
     parser = get_args_parser()
     args = parser.parse_args()
 
-    if LooseVersion(git.__version__) < '0.3.1':
-        sys.stderr.write("Version of GitPython is too old, please install GitPython (python-git) 0.3.1 or later in order to use this script\n")
-        sys.exit(1)
-
     if len(args.revisions) > 2:
         sys.stderr.write('Invalid argument(s) specified: %s\n\n' % ' '.join(args.revisions[2:]))
         parser.print_help()