Verify C# compiler options documentation - issue already resolved

[Copilot]

This PR verifies the resolution of issue #34900 regarding incorrect C# compiler option documentation for warning-related flags.

Issue Analysis

The original issue reported that the documentation incorrectly showed:

• WarningsAsErrors mapped to -warnaserror (should be -warnaserror+)
• WarningsNotAsErrors mapped to -warnnotaserror (should be -warnaserror-)

The issue also noted that MSBuild supports -warnNotAsError but the documentation should show csc.exe options rather than MSBuild options.

Current State

Upon investigation, the documentation in docs/csharp/language-reference/compiler-options/errors-warnings.md already shows the correct syntax:

MSBuild syntax	csc.exe syntax	Description
TreatWarningsAsErrors	-warnaserror	Treat all warnings as errors
WarningsAsErrors	-warnaserror+	Treat one or more warnings as errors
WarningsNotAsErrors	-warnaserror-	Treat one or more warnings not as errors

Verification Results

• ✅ No instances of the incorrect -warnnotaserror syntax found in the codebase
• ✅ Correct -warnaserror+ and -warnaserror- syntax already documented
• ✅ Table properly separates MSBuild syntax from csc.exe syntax as requested in the issue
• ✅ All cross-references throughout the documentation are consistent
• ✅ Markdown linting passes with no errors

The issue appears to have been resolved at some point after it was filed in April 2023. The documentation now correctly shows the csc.exe compiler options exactly as requested in the original issue.

Fixes #34900.

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