fix: Colors for variable, function and constant should be different

[andrewnester]

Issue #, if available: #4800

Description of changes:
Some changes for themes such as Tomorrow Night and etc have been introduced here: 87ad55d

But these changes are actually not so good to distinguish between variables, functions and constants. So reverting them back.

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[codecov]

Codecov Report

Merging #4802 (4f046af) into master (7a4f9e2) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4802   +/-   ##
=======================================
  Coverage   71.12%   71.12%           
=======================================
  Files         554      554           
  Lines       55711    55711           
  Branches    10419    10419           
=======================================
  Hits        39622    39622           
  Misses      16089    16089           

Flag	Coverage Δ
unittests	71.12% <ø> (ø)

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