Some nullable parameters are null-checked

[RikkiGibson]

roslyn/src/Workspaces/Core/Portable/Workspace/Workspace_Registration.cs

Lines 78 to 83 in 6be7f04

	public static WorkspaceRegistration GetWorkspaceRegistration(SourceTextContainer? textContainer)
	{
	if (textContainer == null)
	{
	throw new ArgumentNullException(nameof(textContainer));
	}

roslyn/src/Features/LanguageServer/Protocol/Extensions/ProtocolConversions.cs

Lines 144 to 147 in 6be7f04

	public static Uri GetUriFromFilePath(string? filePath)
	{
	if (filePath is null)
	throw new ArgumentNullException(nameof(filePath));

cc @genlu @dibarbet @CyrusNajmabadi

It seems like if the parameter type allows null, then the parameter should not be null checked.