libfs_avb_internal_test & libfs_avb_test already run in presubmit

remove duplicate postsubmit setup, they already run in host-unit-tests presubmit

Change-Id: I4065d7a50729a14911ec64f10082987d3f9ddcfc
Test:presubmit
Bug: 183622274
diff --git a/fs_mgr/libfs_avb/TEST_MAPPING b/fs_mgr/libfs_avb/TEST_MAPPING
deleted file mode 100644
index b0f36d4..0000000
--- a/fs_mgr/libfs_avb/TEST_MAPPING
+++ /dev/null
@@ -1,12 +0,0 @@
-{
-  "postsubmit": [
-    {
-      "name": "libfs_avb_test",
-      "host": true
-    },
-    {
-      "name": "libfs_avb_internal_test",
-      "host": true
-    }
-  ]
-}