chore: remove deprecated Google UA tracking id

[slorber]

Motivation

The UA tracking id is now useless.

We can see in practice no data is collected anymore by this tracker:

See also #7221

Google Analytics 4 has replaced Universal Analytics

Google Analytics 4 is our next-generation measurement solution, and it has replaced Universal Analytics. Starting on July 1, 2023, standard Universal Analytics properties stopped processing new data. To maintain your website measurement, you'll need a Google Analytics 4 property. Learn how to make the switch to Google Analytics 4

Test Plan

local (analytics are disabled in previews)

Test links

Deploy preview: https://deploy-preview-_____--docusaurus-2.netlify.app/

[netlify]

✅ [V2]

Name	Link
🔨 Latest commit	1bd2645
🔍 Latest deploy log	https://app.netlify.com/sites/docusaurus-2/deploys/6522e4716f7e050008d15138
😎 Deploy Preview	https://deploy-preview-9384--docusaurus-2.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
/	🟠 66	🟢 97	🟢 92	🟢 100	🟠 89	Report
/docs/installation	🟠 85	🟢 98	🟢 92	🟢 100	🟠 89	Report

[github-actions]

Size Change: -95 B (0%)

Total Size: 1.13 MB

Filename	Size	Change
website/build/assets/js/main.********.js	861 kB	-34 B (0%)
website/build/index.html	41.4 kB	-35 B (0%)

ℹ️ View Unchanged

Filename	Size	Change
website/.docusaurus/globalData.json	117 kB	-26 B (0%)
website/build/assets/css/styles.********.css	113 kB	0 B

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