Remove deprecated methods from CustomResource class

[manusa]

Description

Part of #6602

The following methods are deprecated and no longer used, they must be removed the CustomResource class:

kubernetes-client/kubernetes-client-api/src/main/java/io/fabric8/kubernetes/client/CustomResource.java

Lines 207 to 213 in 32b3473

	/**
	* @deprecated use {@link HasMetadata#getPlural(Class)} instead
	*/
	@Deprecated
	public static String getPlural(Class<?> clazz) {
	return HasMetadata.getPlural(clazz);
	}

kubernetes-client/kubernetes-client-api/src/main/java/io/fabric8/kubernetes/client/CustomResource.java

Lines 221 to 227 in 32b3473

	/**
	* @deprecated use {@link HasMetadata#getSingular(Class)} instead
	*/
	@Deprecated
	public static String getSingular(Class<?> clazz) {
	return HasMetadata.getSingular(clazz);
	}

[currantino]

Hey, I'm ready to fix this