Fix Group Notification expand button clipping text when the system font size is at maximum

Fixes the visually clipped text of Group Notification expand button - children count, when the Accessibility - Display size and text - font size is at its maximum.

Test: Manual, Go to Settings > Accessibility > Display size and text. Adjust the "Font size" to the biggest. Post a Group Notification, then open the Shade. The Group Notification's expand button text shouldn't be clipped.
Bug: 264009793
Bug: 273401782
Change-Id: I1c6afac818f4ceba6b5c7d78a6c75a941b77cc3e