Remove `testhat::` prefix

[donyunardi]

teal.picks/tests/testthat/test-badge_dropdown.R

Line 26 in d654b02

testthat::expect_visible("#test-inputs-inputs_container", app_driver = app_driver)

This line is supposed to be using the expect_visible function from teal.picks, not testthat

https://github.com/insightsengineering/teal.picks/blob/main/tests/testthat/helper-shinytest2.R#L15

With the current state, we got an error:

Error in testthat::expect_visible("#test-inputs-inputs_container", app_driver = app_driver) : 
  unused argument (app_driver = app_driver)

We need to remove prefix.