fix: replace NodeList.foreach with for loop

[InspiredGuy]

Issue #, if available:
#5766

Description of changes:
Fix for old browsers. Replace NodeList.forEach() with for loop, since forEach is not available before Firefox 50 (see docs).

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Pull Request Checklist:

• No backwards incompatible changes were made to Ace's public interface which is defined through the main typings file (ace.d.ts) and its references:
  • https://github.com/ajaxorg/ace/blob/master/ace.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-modes.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-extensions.d.ts

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.10%. Comparing base (cd78a94) to head (2ffd5ee).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5769   +/-   ##
=======================================
  Coverage   87.10%   87.10%           
=======================================
  Files         602      602           
  Lines       44092    44092           
  Branches     7234     7234           
=======================================
  Hits        38407    38407           
  Misses       5685     5685           

Flag	Coverage Δ
unittests	87.10% <100.00%> (ø)

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