Remove cached types from HelpWriter

[akamsteeg]

In HelpWriter, we cache the types of DisplayAttribute and RequiredAttribute but that serves no purpose besides making the object bigger.

AtleX.CommandLineArguments/src/AtleX.CommandLineArguments/Help/HelpWriter.cs

Lines 14 to 22 in b3934ee

	/// <summary>
	/// Gets the cached <see cref="Type"/> of <see cref="DisplayAttribute"/>
	/// </summary>
	private readonly Type cachedDisplayAttributeType;
	/// <summary>
	/// Gets the cached <see cref="Type"/> of <see cref="RequiredAttribute"/>
	/// </summary>
	private readonly Type cachedRequiredAttributeType;

We should remove those cached instances.