Remove the text from the undo button

This helps to keep space available for the Edit mode title on larger display sizes and different locales
Also center the text of the grid header as a drive by fix

Test: manually undoing changes
Flag: com.android.systemui.qs_ui_refactor_compose_fragment
Fixes: 417535281
Change-Id: Ibe33306d84f42022a9b23b6f966c1512e02f3c26