Calendar button is not well aligned with firefox

[simeoreig]

To reproduce the error it is only necessary to go to https://www.primefaces.org/primeblocks-jsf/application/formlayout.xhtml and view the third form with Firefox. The buttons on the calendar control are misaligned. It doesn't happen with chrome or chromium.

Calendar control button works correctly outside of Primeblocks http://primefaces.org/showcase/ui/input/calendar/calendar.xhtml.

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