fix: Selenium and Playwright examples to be more comparable

[guolau]

Affected Components

• Content & Marketing
• Pricing
• Test
• Docs
• Learn
• Other

Notes for the Reviewer

This is a small change to our Selenium vs Playwright page (/comparisons/frameworks/playwright-vs-selenium)

User mentioned that we claim the Selenium example is doing the same thing as the Playwright example, but that was not the case. I updated both examples to address this and updated the PWT example to use Playwright Test.

ref: https://linear.app/checklyhq/issue/DOC-25/selenium-example-is-not-doing-the-same-thing-as-the-playwright-example