fix: remove unused TestContext

[robertkowalski]

The function WithTestContext is never called in the project, and
there is just one usage of TestContext, inside one of our loggers

[codecov]

Codecov Report

Merging #1013 (64ebcb7) into master (4f8da0a) will increase coverage by 1.39%.
The diff coverage is 80.55%.

@@            Coverage Diff             @@
##           master    #1013      +/-   ##
==========================================
+ Coverage   57.50%   58.90%   +1.39%     
==========================================
  Files          32       33       +1     
  Lines        4594     4645      +51     
==========================================
+ Hits         2642     2736      +94     
+ Misses       1729     1681      -48     
- Partials      223      228       +5     

Impacted Files	Coverage Δ
pkg/model/action.go	0.00% <ø> (ø)
pkg/model/planner.go	50.73% <ø> (+0.32%)	⬆️
pkg/exprparser/interpreter.go	74.39% <66.66%> (+0.99%)	⬆️
pkg/runner/logger.go	66.00% <67.56%> (+0.56%)	⬆️
pkg/runner/runner.go	74.52% <75.00%> (-1.95%)	⬇️
pkg/runner/expression.go	89.36% <77.61%> (-1.46%)	⬇️
pkg/runner/job_executor.go	82.50% <82.50%> (ø)
pkg/runner/step_context.go	85.81% <84.00%> (+4.17%)	⬆️
pkg/runner/action.go	84.21% <84.21%> (ø)
pkg/runner/run_context.go	80.03% <96.15%> (+0.38%)	⬆️
... and 9 more

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[ZauberNerd]

A bit of context: We've introduced the TestContext here: #859, which then got reverted: #890 and rewritten: #898
It was initially introduced to allow assertions on log output in our first pre/post PR: https://github.com/nektos/act/pull/861/files#diff-1f71c031405f1ee099e0d3fc42613897dcb824213ab0a09321420b4e9ecb0cddR294-R381

[mergify]

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[mergify]

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