Fix a QA instability in the maven scenario

🍉 Context

In #344843 (closed), it has been detected that an example of the maven QA scenario failed quite consistently.

The example is part of a context that has two examples:

1. Switch the allow duplicates setting on, upload a duplicated package and check that it's successful
2. Switch the allow duplicates setting off, upload a duplicated package and check that it's not successful

Here is the UI where the setting is for maven packages:

🔥 Problem

The issue lies in the helpers used to manipulate the setting toggle.

It seems that the #click_element function doesn't work when the setting is off and we click on it.

Screen_Recording_2021-11-05_at_13.01.28

🔬 What does this MR do and why?

• Update the helpers function to actually #click on the button itself
• Update how the button state is checked
  • It was done through a label content but it would be more reliable to check the css classes on the button.

📷 Screenshots or screen recordings

$ WEBDRIVER_HEADLESS=false bundle exec bin/qa Test::Instance::All http://172.16.123.1:8000 -- qa/specs/features/browser_ui/5_package/package_registry/maven_repository_spec.rb --tag orchestrated --tag packages

[...snip...]

Finished in 11 minutes 35 seconds (files took 8.39 seconds to load)
3 examples, 0 failures

Randomized with seed 50164

⚗ How to set up and validate locally

1. Pull the MR branch
2. Run the maven QA scenario as above

🛃 MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.