Fix regression introduced by 175f33ed8. 'expanding' property set to true
was ignored when QStyle::styleHint() returned Qt::AlignRight for
SH_TabBar_Alignment.
When we calculate tabs geometry, we put an empty tab at the front and
back and set its expansive attribute depending on tab alignment AND
'expanding' property.
Task-number: QTBUG-61480
Change-Id: I6a1827ae8a3f2c6bee5124c18c7f2b1c0a7862f3
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@qt.io>
