Revert "Make build property CompilerGeneratedFilesOutputPath accessible to Roslyn project"

[drewnoakes]

Reverts #9544

This change was triggering a failure in Roslyn around use of EmitCompilerGeneratedFiles, leading to project faults resembling:

System.ArgumentException: Absolute path expected
Parameter name: path
  at Microsoft.CodeAnalysis.CompilationOutputInfo.WithGeneratedFilesOutputDirectory(String path)
  at Microsoft.CodeAnalysis.Workspaces.ProjectSystem.ProjectSystemProject.<>c__DisplayClass69_0.<set_GeneratedFilesOutputDirectory>b__0(Solution s)
...

At the start of October, Roslyn started requiring an absolute path here:

https://github.com/dotnet/roslyn/pull/75311/files#diff-8440787c9215f81fa8cabe9072d5ab0598251313a4480cfca075041ceed8a5bbR41-R44

But by default, the SDK provides a relative path (and indeed all online examples show relative paths here). Only once we inserted #9544

@tmat has a PR open in Roslyn to fix this: https://github.com/dotnet/roslyn/pull/75674/files

Once the Roslyn side is fixed, we can reinstate this change.

Microsoft Reviewers: Open in CodeFlow