Standarddialogs example: Remove horizontal spacer from fullscreen layout.

It does not work as expected since the QLineEdits do not expand.
Amends b880b7e1

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Change-Id: I0b3b3822cca7fc6442a7155eecd46bd3d134d069
Reviewed-by: Shawn Rutledge <shawn.rutledge@theqtcompany.com>