Fix primary button description text
Fix primary button description text

It's also confusing that oojs-ui uses primary which has been deprecated
in favour of progressive in mediawiki-ui.

Change-Id: I2a7aca4538ec02464b48a2f3584a89d054be24e8

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui