WifiMigrationTest: Remove all usage of WifiMigration.loadFromStore

In preparation of moving away from this API surface to a different
mechanism.

Bug: 149418926
Test: atest android.net.wifi.cts
Change-Id: I5805d9dc27a248b633d514356f603f63af799429
1 file changed
tree: 3bf8386041415c0ded4bb6e8964030c1a1b96978
  1. tests/