Revert "[ENH] Allow MED format for iEEG data (*_ieeg.medd/) (#1956)"

[effigies]

This reverts commit 436d7cd.

Adding this format needs additional vetting, per steering group decision.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.06%. Comparing base (ac11483) to head (e01ebb5).
⚠️ Report is 231 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2122   +/-   ##
=======================================
  Coverage   82.06%   82.06%           
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  Files          17       17           
  Lines        1533     1533           
=======================================
  Hits         1258     1258           
  Misses        275      275           

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[ericearl]

These removals look correct to me.