Fix row layout warnings for DateTime page in settings app

The following warning is repeatedly seen on the journal for datetime section on settings app:

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Jul 05 20:18:35 intel-corei7-64 afbd-settings@0.1[1304]: qrc:/datetime/DateTime.qml:38:9: QML RowLayout: Detected anchors on an item that is managed by a layout. This is undefined behavior; use Layout.alignment instead.

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The anchoring needs updating.