fix typo in RenderTarget::build attachment size validation
fix typo in RenderTarget::build attachment size validation

the validation could fail if attachments used different LODs but the
sizes still matched.

google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament