appview/topbar: switch "+ new" button from primary to secondary

having a primary call to action always present in the nav bar was
creating issues with other call to actions at a hierarchical level
this change prevents buttons clashing against each other because of
their level of importance

*As a rule of thumb, the main call to action on a page should be
heaviest in weight when compared to other buttons and/or links. All
other action items should appear secondary in terms of color, placement,
shape, and overall weight allocation.*

refs:
-
https://www.smashingmagazine.com/2009/10/call-to-action-buttons-examples-and-best-practices/#offer-secondary-alternative-actions

-
https://uxmag.com/articles/usability-tip-one-main-call-to-action-item-per-task#:~:text=As%20a%20rule,to%20move%20forward.

Signed-off-by: eti <eti@eti.tf>