update metric thresholds for Lighthouse 8

[brendankenny]

Lighthouse 8 was just released and brought new score thresholds for total-blocking-time and first-contentful-paint and a re-weighting of the overall performance score.

I also noticed that the speed-index thresholds were incorrect and the screenshots were out of date (showing old metrics), so I updated those and a few random obsolete links.

This isn't the full revamp some of these articles need, but that can wait for the migration to d.c.c (or whatever we decide to do there).

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Requested changes

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src/site/content/en/lighthouse-performance/first-contentful-paint/index.md

• Please change your usage of the following words:
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src/site/content/en/lighthouse-performance/interactive/index.md

• Please change your usage of the following words:
  • Do not use master. Affected lines: 118

src/site/content/en/lighthouse-performance/lighthouse-largest-contentful-paint/index.md

• Please change your usage of the following words:
  • Do not use master. Affected lines: 70

src/site/content/en/lighthouse-performance/lighthouse-total-blocking-time/index.md

• Please change your usage of the following words:
  • Do not use master. Affected lines: 90

src/site/content/en/lighthouse-performance/performance-scoring/index.md

• Please break lines at 100 characters maximum. Long lines can be difficult to work with in GitHub's pull request UI. The following tools can help speed up the process: Rewrap (VS Code), Docs To X (Google Docs; only available for Googlers). Affected lines: 16, 20, 29, 39, 44, 51, 54, 140, 150, 154, 163, 173, 176, 178, 182
• Please put a blank line before and after each section heading. Some Markdown parsers don't detect the text as a section heading unless there is blank space before and after it. Affected lines: 175
• Please change your usage of the following words:
  • Do not use master. Affected lines: 29

src/site/content/en/lighthouse-performance/speed-index/index.md

• Please change your usage of the following words:
  • Do not use master. Affected lines: 85

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[brendankenny]

Requested changes

If there are any common problems with the content files you created or modified, they will be listed here.

all of these were pre-existing and not touched by this PR

• Most of them are due to lighthouse unfortunately not migrating to main yet, so there's not much that can be done there yet
• The line-length issues aren't on any of the changed lines and would add a lot to the PR diff, but I could take a pass at that if it's important

[brendankenny]

these have been removed on the newer metric pages (e.g. https://web.dev/lighthouse-total-blocking-time/#how-lighthouse-determines-your-tbt-score) and Lighthouse doesn't expose the per-metric score directly (just in the raw JSON response), so it seemed good to remove them (otherwise they need to be updated to 90-100)

[brendankenny]

Lighthouse moved off SSIM in GoogleChrome/lighthouse#4980