Remove @Postsubmit annotations

Since they have been replaced with @FlakyTest we can remove the
annotation and import.

Change-Id: I3493f9c56c1b978367e7fa26fc6a9018e9c36586
Merged-In: I3493f9c56c1b978367e7fa26fc6a9018e9c36586
Fixes: 35710737
Test: No change to behavior
1 file changed