docs: remove Twitter and X references

[jasperdevs]

Closes #156.

Summary

• Remove Angular Hispano X link from shared link constants, footer, and navigation social menu
• Remove X/Twitter release-notification text from the update docs in Spanish and English

Verification

• npm ci with Node 22.22.3
• git diff --check
• rg -n "x\.com|Twitter|twitter|ngLinks\.X|X \(formerly|antes Twitter|anteriormente Twitter|@angular en X|@angular on X" adev-es/src/app/core adev-es/src/content/best-practices/update*.md returned no matches

Note: I started npm run build, but stopped it after it spent ~20 minutes building the full upstream Angular/Bazel production target rather than this repo-specific docs surface.

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[Splaktar]

Many thanks for your contribution! We need a few minor tweaks to the code submitted.

Then we also need the CLA signed, and the commit signed (more on GitHub signed commits here).

[Splaktar]

The .en files are the original English files before being translated. We don't need to keep them updated like this. They aren't used/rendered. They are just kept to reference changes so we know what might need re-translation.

[Splaktar]

Same, we don't want to update these .en files.

[Splaktar]

Please revert.

[Splaktar]

Please add the following to the commit message:

Fixes #156.