Azure.Core.Tests has uncompilable snippets

[heaths]

When passing the SNIPPET symbol to build snippets and make sure they are valid, this project yields errors.

You can repro this issue by running:

dotnet build eng/service.proj -warnaserror /t:rebuild /p:DebugType=none /p:SDKType=all /p:ServiceDirectory=core /p:IncludePerf=false /p:IncludeStress=false /p:PublicSign=false /p:Configuration=Release /p:EnableSourceLink=false /p:BuildSnippets=true

When resolved, please remove the BuildSnippets: false line from sdk/core/ci.yml.

See #33969 for more context.