[Notif redesign] Update title size in expanded notifs

Previously, it was 16sp when expanded but 14sp when collapsed. With this
change, it is 14sp across the board.

Note that notification_2025_title.xml is a fork of notification_template_part_line1.xml.

Bug: 378660052
Test: visual test + screenshot tests
Flag: android.app.notifications_redesign_templates
Change-Id: I394ebaa70e568acbed8f37c15ba22eef90340cb5