chore: Cleanup tests and fix spellings

[filzrev]

What's included in this PR

• Fix spelling miss in verbose log message from week type to `weak type".
• Remove code that explicitly setting ServicePointManager.SecurityProtocol to Tls12
  Because there are no supported OS/.NET versions that require this settings.
• Remove TestSchemaReachedLimits tests. Because Json.NET schema is not used anymore.
• Rename test method signature and traits that using Markdig.
• Modify skipped tests. that pass tests with small modifications.
• Remove TestMetadataCommandFromCSProjectWithVsinstalldirEnvSet test because it's not actually used.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.01% ⚠️

Comparison is base (706a10c) 77.58% compared to head (b6f89b1) 77.58%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9091      +/-   ##
==========================================
- Coverage   77.58%   77.58%   -0.01%     
==========================================
  Files         592      592              
  Lines       24608    24608              
==========================================
- Hits        19092    19091       -1     
- Misses       5516     5517       +1     

Files Changed	Coverage Δ
src/Docfx.Build.SchemaDriven/OverwriteApplier.cs	96.15% <ø> (ø)
src/Docfx.Build.Engine/ManifestProcessor.cs	94.53% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[yufeih]

Looks great!