[Notif redesign] Rename notification_2025_template_text.xml to notification_2025_text.xml

This is to match the naming convention of the other notification layouts.

Bug: 380465801
Change-Id: I99333901a7de87e9ccb75edcb2e4bdd19ad2fdbb
Test: Presubmit
Flag: android.app.notifications_redesign_templates