Rename "capture own screenshot" flag again

Adding metadata{} to the flag after the first commit is not
supported by the release tooling and breaks the flag process.

Change-Id: I9c3b7efb4273ed73c230ac70041f803c8b5eb38d
Flag: android.app.contextualsearch.flags.contextual_search_prevent_self_capture
Test: GtsInteractiveContextualSearchIntentTestCases
Bug: 390176823