Use python3

python2 is EOL, specify the python scripts to use python3.

Tested: Verify it builds fine in local CI. With bitbake recipe changes,
        verify it builds OK with python3native.

Signed-off-by: Lei YU <mine260309@gmail.com>
Change-Id: Icd5d10193e9323bbdbcd854e9027e014e01a1829
diff --git a/phosphor-regulators/tools/validate-regulators-config.py b/phosphor-regulators/tools/validate-regulators-config.py
index bca989d..7b1cd6f 100755
--- a/phosphor-regulators/tools/validate-regulators-config.py
+++ b/phosphor-regulators/tools/validate-regulators-config.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 import argparse
 import json