[Bug] Fix vocabs and add corresponding test case

[felixdittrich92]

This PR:

• fix duplications in hindi and vietnamese vocabs
• update docs
• add corresponding test case

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.60%. Comparing base (9b6dea3) to head (e5e9d9b).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1813   +/-   ##
=======================================
  Coverage   96.60%   96.60%           
=======================================
  Files         165      165           
  Lines        7929     7929           
=======================================
  Hits         7660     7660           
  Misses        269      269           

Flag	Coverage Δ
unittests	96.60% <ø> (ø)

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