Demote apkdmverity tests to postsubmit

The tests are known to be flaky.

Bug: 223769777
Test: N/A
Change-Id: I4914fbcc52dcb0ca998a7f709bfec9d05e184f5a
diff --git a/apkdmverity/TEST_MAPPING b/apkdmverity/TEST_MAPPING
index 1bbec76..997b3f9 100644
--- a/apkdmverity/TEST_MAPPING
+++ b/apkdmverity/TEST_MAPPING
@@ -1,5 +1,5 @@
 {
-  "presubmit" : [
+  "postsubmit" : [
     {
       "name" : "apkdmverity.test"
     }