Remove gccfilter in favor of the default feature of GCC and Clang

[jslee02]

gccfilter was used to colorize the compiler output, but the feature is now supported by GCC and Clang by default.

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Before creating a pull request

• Document new methods and classes
• Format new code files using clang-format

Before merging a pull request

• Set version target by selecting a milestone on the right side
• Summarize this change in CHANGELOG.md
• (N/A) Add unit test(s) for this change

[codecov]

Codecov Report

Merging #1464 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1464      +/-   ##
==========================================
+ Coverage   58.23%   58.24%   +0.01%     
==========================================
  Files         412      412              
  Lines       29928    29928              
==========================================
+ Hits        17429    17432       +3     
+ Misses      12499    12496       -3     

Impacted Files	Coverage Δ
dart/dynamics/Skeleton.cpp	66.33% <0.00%> (+0.16%)	⬆️