chore(docs): update docs link titles

[ShGKme]

☑️ Resolves

• v6 and v7 are unmaintained for a long time now, having these links in the main menu doesn't seem necessary
  • If we still want to have the links available, we can either add them to README of the corresponding branches or list all the old links in "Other versions"
• v9 is not next anymore, but the current latest
• v8 is not current anymore but so called stable (actually, also current, but for Vue 2 apps)
• Removed .x to make it simpler and shorter

🖼️ Screenshots

🏚️ Before	🏡 After

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable
• 2️⃣ Backport to stable8 for maintained Vue 2 version or not applicable

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 51.57%. Comparing base (e14b022) to head (110e134).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7768   +/-   ##
=======================================
  Coverage   51.57%   51.57%           
=======================================
  Files          96       96           
  Lines        3141     3141           
  Branches      863      862    -1     
=======================================
  Hits         1620     1620           
  Misses       1273     1273           
  Partials      248      248           

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[ShGKme]

/backport to stable8