Upgrade python version to 3.9

py3-launcher contains a list of dirnames in sys.path that contain
the python version (/my/path/3.8/... vs /my/path/3.9/...). Upgrading
the version should fix the assertions in
https://cs.android.com/android/platform/superproject/+/master:build/soong/python/tests/py-cmd_test.py;l=68-71

(I was unable to test this hypothesis locally, would appreciate feedback
on how to do that)
Test: TH
Bug: 197112964

Change-Id: I41883072c2c8449b136c72c452f15607fb9c8e44
diff --git a/Android.bp b/Android.bp
index 570c9df..db5d4c2 100644
--- a/Android.bp
+++ b/Android.bp
@@ -339,7 +339,7 @@
     name: "py3-launcher-defaults",
     defaults: ["py3-interp-defaults", "cpython3-interp-host-prebuilts"],
     cflags: [
-        "-DVERSION=\"3.8\"",
+        "-DVERSION=\"3.9\"",
         "-DVPATH=\"\"",
         "-DPREFIX=\"\"",
         "-DEXEC_PREFIX=\"\"",