Closes #72: Change the way we load the page for LCP

[Miraeld]

Description

Fixes #72

Documentation

Technical documentation

This PR change the way we are loading the page while running test for LCP. Until now we were waiting 2 seconds before closing the page and load a new one. However, the beacon script now adds an attribute beacon-complete to true once it finishes to run. So this PR changes the 2 seconds by looking for this attribute.

Type of change

• Enhancement (non-breaking change which improves an existing functionality).

New dependencies

Risks

Checklists

Feature validation

• I validated all the Acceptance Criteria. If possible, provide sreenshots or videos.
• I triggered all changed lines of code at least once without new errors/warnings/notices.

Documentation

• I prepared the technical documentation if needed, and shared it in the PR or the GitHub issue.

Code style

• I wrote self-explanatory code about what it does.
• I wrote comments to explain why it does it.
• I named variables and functions explicitely.
• I protected entry points against unexpected inputs.
• I did not introduce unecessary complexity.
• I listed the introduced external dependencies explicitely on the PR.
• I validated the repo-specific guidelines from CONTRIBUTING.md.

[jeawhanlee]

@Miraeld I don't think this needs waiting on QA as it's a really small change that doesn't really affect the major test but I need to know if you tested this and it works as expected before I merge.

[Miraeld]

@jeawhanlee , yea I've tested it and it does work.