Update submodule and remove build copy.

[JimBobSquarePants]

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• I have provided test coverage for my change (where applicable)

Description

Reverts the usage of T4 via a submodule.

[codecov]

Codecov Report

Merging #1142 into master will not change coverage by %.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1142   +/-   ##
=======================================
  Coverage   82.27%   82.27%           
=======================================
  Files         678      678           
  Lines       29216    29216           
  Branches     3278     3278           
=======================================
  Hits        24038    24038           
  Misses       4483     4483           
  Partials      695      695           

Flag	Coverage Δ
#unittests	82.27% <ø> (ø)

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