TAARenderPass: Fix runtime error in `dispose()`. (#26991)

* Fix for dispose error
sampleRenderTarget is being deleted and set to null by super.dispose();
the check for undefined was incorrect causing an attempt to call dispose on a null object.

* Removed disposal of sampleRenderTarget entierly

examples/jsm/postprocessing/TAARenderPass.js

@@ -147,8 +147,7 @@ class TAARenderPass extends SSAARenderPass {
 
 		super.dispose();
 
-		if ( this.sampleRenderTarget !== undefined ) this.sampleRenderTarget.dispose();
-		if ( this.holdRenderTarget !== undefined ) this.holdRenderTarget.dispose();
+		if ( this.holdRenderTarget ) this.holdRenderTarget.dispose();
 
 	}