Increase size of DatabaseImplTest to medium (#4827)

* Increase size of DatabaseImplTest to medium

Was a bit flaky.

* Check flakiness

* Revert presubmit tweak

Author: csilvestrini

javatests/arcs/android/storage/database/BUILD

@@ -9,6 +9,7 @@ package(default_visibility = ["//visibility:public"])
 
 arcs_kt_android_test_suite(
     name = "database",
+    size = "medium",
     manifest = "//java/arcs/android/common:AndroidManifest.xml",
     package = "arcs.android.storage.database",
     deps = [