Remove ignored mutations

[martincostello]

Just curious as to the impact on the mutation tests if we remove this, as Polly.Testing has to manually remove it to get any results at all anyway:

Polly/build.cake

Lines 315 to 318 in 4469d83

	if (moduleName == "Polly.Testing")
	{
	strykerConfigPath = PatchStrykerConfig(strykerConfigPath, (config) => config.Remove("ignore-mutations"));
	}

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.09%. Comparing base (4469d83) to head (94f64c2).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2512   +/-   ##
=======================================
  Coverage   94.09%   94.09%           
=======================================
  Files         311      311           
  Lines        7431     7431           
  Branches     1043     1043           
=======================================
  Hits         6992     6992           
  Misses        342      342           
  Partials       97       97           

Flag	Coverage Δ
linux	94.09% <ø> (ø)
macos	94.09% <ø> (ø)
windows	94.07% <ø> (ø)

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[martincostello]

The coverage we lose with the current settings appear to fall mainly into these buckets:

• Argument validation
• Argument validation where removing it falls through to another overload that has the same checks
• Checking that something that should have been disposed was disposed

Have opened #2514 to fix some of the coverage gaps.