script: specify the interpreter to env

Env is generally more portable than hardcoding path.
This change also keeps all scripts consistent.

Tested: all can run directly.

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: Ia2636420e54fae24a5a339377de65957ed40cc7e
diff --git a/scripts/check_base_registry.py b/scripts/check_base_registry.py
old mode 100644
new mode 100755
index ab4b2e6..1db533a
--- a/scripts/check_base_registry.py
+++ b/scripts/check_base_registry.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python3
+#!/usr/bin/env python3
 
 import argparse
 import json
diff --git a/scripts/parse_registries.py b/scripts/parse_registries.py
index e0eaa3f..3786843 100755
--- a/scripts/parse_registries.py
+++ b/scripts/parse_registries.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python3
+#!/usr/bin/env python3
 import requests
 import zipfile
 from io import BytesIO
diff --git a/scripts/update_schemas.py b/scripts/update_schemas.py
index f324967..01531c8 100755
--- a/scripts/update_schemas.py
+++ b/scripts/update_schemas.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python3
+#!/usr/bin/env python3
 import requests
 import zipfile
 from io import BytesIO