extract_kernel: make it py2/py3 compatible

use py3 for AOSP build, while the script itself can be
executed under py2/py3 environment directly.

TEST: extract info from Pixel 4 kernel

Change-Id: I00db6dabb1ff93f0758017a666c476816caefae7
diff --git a/tools/Android.bp b/tools/Android.bp
index e0f3739..357ee2a 100644
--- a/tools/Android.bp
+++ b/tools/Android.bp
@@ -62,10 +62,10 @@
   srcs: ["extract_kernel.py"],
   version: {
     py2: {
-      enabled: true,
+      enabled: false,
     },
     py3: {
-      enabled: false,
+      enabled: true,
     },
   },
 }