[ENH] Updated HED Version to 8.4.0 in examples

[VisLab]

Updated specification to use latest HED version in the examples.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.71%. Comparing base (d62a5d2) to head (66d2e06).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2237   +/-   ##
=======================================
  Coverage   82.71%   82.71%           
=======================================
  Files          20       20           
  Lines        1608     1608           
=======================================
  Hits         1330     1330           
  Misses        278      278           

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