Update art_apex_test.py to use python3.

Note that the interpreter specification in that script is
irrelevant. The `python_binary_host` definition in the
Android.bp defines what interpreter is actually used.

Test: m art-check-release-apex-gen
Change-Id: I9abd12a1956fabe415ce3e06422022a3975f2b34
diff --git a/build/apex/Android.bp b/build/apex/Android.bp
index b911637..0f9a87f 100644
--- a/build/apex/Android.bp
+++ b/build/apex/Android.bp
@@ -437,14 +437,6 @@
     name: "art-apex-tester",
     srcs: ["art_apex_test.py"],
     main: "art_apex_test.py",
-    version: {
-        py2: {
-            enabled: true,
-        },
-        py3: {
-            enabled: false,
-        },
-    },
 }
 
 // Genrules so we can run the checker, and empty Java library so that it gets executed.
diff --git a/build/apex/art_apex_test.py b/build/apex/art_apex_test.py
index 87be4b3..3eeb7fc 100755
--- a/build/apex/art_apex_test.py
+++ b/build/apex/art_apex_test.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # Copyright (C) 2019 The Android Open Source Project