Clear TaskInfo#capturedLink when filling task info

TaskInfo objects are sometimes reused and the captured link needs to be
cleared so that it is not shared from other tasks.

Bug: 349695493
Test: Open slides from gmail app and use button to switch to browser
Flag: com.android.window.flags.enable_desktop_windowing_app_to_web
Change-Id: I6968d48ee6293a33944eff071e5232119d0a370a