Remove CAS attributes from snippets

[gewarren]

Contributes to dotnet/docs#29143.

[opbld34]

Docs Build status updates of commit 08232d1:

✅ Validation status: passed

File	Status	Preview URL	Details
snippets/csharp/System.ComponentModel.Design/DesignerActionHeaderItem/Overview/designeractions.cs	✅Succeeded	View
snippets/csharp/System.ComponentModel.Design/DesignerCollection/Overview/examplecomponent.cs	✅Succeeded	View
snippets/csharp/System.ComponentModel.Design/DesignerVerbCollection/Overview/class1.cs	✅Succeeded	View
snippets/csharp/System.ComponentModel.Design/IDesigner/Overview/testcontrol.cs	✅Succeeded	View
snippets/csharp/System.ComponentModel.Design/IDesignerFilter/Overview/controldesignerexample.cs	✅Succeeded	View
snippets/csharp/System.ComponentModel.Design/IDesignerHost/Overview/idesignerhostexample.cs	✅Succeeded	View
snippets/csharp/System.ComponentModel.Design/IEventBindingService/Overview/source.cs	✅Succeeded	View
snippets/csharp/System.ComponentModel.Design/IMenuCommandService/Overview/component1.cs	✅Succeeded	View
snippets/csharp/System.ComponentModel.Design/ITypeResolutionService/Overview/ityperesolutionservicecontrol.cs	✅Succeeded	View
snippets/csharp/System.ComponentModel/IExtenderProvider/Overview/HelpLabel.cs	✅Succeeded	View
snippets/csharp/System.ComponentModel/PropertyTabAttribute/Overview/class1.cs	✅Succeeded	View
snippets/csharp/System.ComponentModel/ToolboxItemFilterAttribute/Overview/samplecontrol.cs	✅Succeeded	View
snippets/csharp/System.ComponentModel/TypeDescriptor/GetProperties/Form1.cs	✅Succeeded	View
snippets/csharp/System.Deployment.Application/ApplicationDeployment/DownloadFileGroup/Form1.cs	✅Succeeded	View
snippets/csharp/System.Deployment.Application/ApplicationDeployment/DownloadFileGroup/Makefile	✅Succeeded
snippets/csharp/System.Deployment.Application/ApplicationDeployment/DownloadFileGroup/Project.csproj	✅Succeeded
snippets/csharp/System.Deployment.Application/ApplicationDeployment/Overview/Form1.cs	✅Succeeded	View
snippets/csharp/System.IO.IsolatedStorage/IsolatedStorageFile/Close/Project.csproj	✅Succeeded
snippets/csharp/System.IO.IsolatedStorage/IsolatedStorageFile/Close/source.cs	✅Succeeded	View
snippets/csharp/System.IO.Packaging/PackageStore/AddPackage/Window1.xaml.cs	✅Succeeded	View
snippets/csharp/System.IO/StreamWriter/AutoFlush/logger.cs	✅Succeeded	View
snippets/csharp/System.IdentityModel.Services/ClaimsPrincipalPermission/Overview/app.config	✅Succeeded
snippets/csharp/System.IdentityModel.Services/ClaimsPrincipalPermission/Overview/program.cs	✅Succeeded	View
snippets/csharp/System.IdentityModel.Services/ClaimsPrincipalPermission/Overview/wifcppwithcam.csproj	✅Succeeded
snippets/csharp/System.IdentityModel.Services/SessionAuthenticationModule/Overview/contact.aspx.cs	✅Succeeded

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