Fix Sign out button's text alignment

Because of limited vertical space in status bar, if user's font size
was increased, Sign out button's text on status bar was not aligned
properly. Adding wrapContentHeight(unbounded=true) modifier lets button's
text align properly when Button composable height is less than Text
composable height.

Test: manual - Sign out button visible on Keyguard's status bar
Test: manual - Increase user's font size - button is properly aligned
Flag: com.android.systemui.sign_out_button_on_keyguard_status_bar
Bug: 392052370
Change-Id: I7f5fa9bf3306640607bfe1c93fe2ffce876f90a4