TextClassificationManager: Update model file reference.

Location of the model files have moved to etc/textclassifier

Test: cts-tradefed run cts-dev -m CtsViewTestCases -t
android.view.textclassifier.cts.TextClassificationManagerTest
Bug: 34865247

Change-Id: I1e9b3a6588b37ce9a35fb5146a3e6dca921510ed