Update reportgenerator to v5.1.21

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
ReportGenerator	nuget	patch	5.1.20 -> 5.1.21
dotnet-reportgenerator-globaltool	nuget	patch	5.1.20 -> 5.1.21

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Release Notes

danielpalme/ReportGenerator

v5.1.21: ReportGenerator_5.1.21

This release requires .NET 4.7 or .NET Core 3.1/5.x/6.x/7.x.

Changes:

• #​606 Improved Cobertura output (complexity metric)

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Configuration

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🚦 Automerge: Enabled.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about these updates again.

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• If you want to rebase/retry this PR, check this box

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[codecov]

Codecov Report

Merging #977 (87201f5) into master (8a12bf5) will decrease coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #977      +/-   ##
==========================================
- Coverage   69.72%   69.69%   -0.04%     
==========================================
  Files         493      493              
  Lines       20066    20066              
  Branches     1603     1603              
==========================================
- Hits        13991    13984       -7     
- Misses       6075     6082       +7     

see 3 files with indirect coverage changes