fix ambiguous call to string.Split

[agollivermsft]

DEPENDS ON: #2286 (update from net472 to net8.0 on windows)

On an Ubuntu 24.04 image I get from work ./src/linux/Packaging.Linux/install-from-source.sh fails with

dotnet --version
8.0.124

MSBuild version 17.8.49+7806cbf7b for .NET
  Determining projects to restore...
  Restored /tmp/tmp.LyZev1gOKL/src/linux/Packaging.Linux/Packaging.Linux.csproj (in 361 ms).
  Restored /tmp/tmp.LyZev1gOKL/src/shared/Microsoft.AzureRepos/Microsoft.AzureRepos.csproj (in 5.46 sec).
  Restored /tmp/tmp.LyZev1gOKL/src/shared/Core/Core.csproj (in 5.46 sec).
  Restored /tmp/tmp.LyZev1gOKL/src/shared/Atlassian.Bitbucket/Atlassian.Bitbucket.csproj (in 5.46 sec).
  Restored /tmp/tmp.LyZev1gOKL/src/shared/GitHub/GitHub.csproj (in 5.46 sec).
  Restored /tmp/tmp.LyZev1gOKL/src/shared/GitLab/GitLab.csproj (in 5.46 sec).
  Restored /tmp/tmp.LyZev1gOKL/src/shared/Git-Credential-Manager/Git-Credential-Manager.csproj (in 7.67 sec).
/tmp/tmp.LyZev1gOKL/src/shared/Core/Interop/Linux/LinuxConfigParser.cs(34,45): error CS0121: The call is ambiguous between the following methods or properties: 'string.Split(char[]?, StringSplitOptions)' and 'string.Split(string?, StringSplitOptions)' [/tmp/tmp.LyZev1gOKL/src/shared/Core/Core.csproj::TargetFramework=net8.0]

Build FAILED.

/tmp/tmp.LyZev1gOKL/src/shared/Core/Interop/Linux/LinuxConfigParser.cs(34,45): error CS0121: The call is ambiguous between the following methods or properties: 'string.Split(char[]?, StringSplitOptions)' and 'string.Split(string?, StringSplitOptions)' [/tmp/tmp.LyZev1gOKL/src/shared/Core/Core.csproj::TargetFramework=net8.0]
    0 Warning(s)
    1 Error(s)

Time Elapsed 00:00:17.29

I don't know much C#, but this change got it to compile & it seems to work locally (I was able to use g-c-m installed from this branch to push this PR, at least)

[agollivermsft]

hmm... so now it works on my ubuntu machine (and linux CI generally), but not on windows. Curious.

[mjcheetham]

This has bene addressed in #2287