[GR-23791] Do not report polymorphism for MetaClassNode

* This caused excessive splitting and is much less needed since we can
  now read the metaClass directly as a field of RubyDynamicObject instead
  of inline caching on the Shape.

Author: eregon

src/main/java/org/truffleruby/language/objects/MetaClassNode.java

@@ -9,7 +9,6 @@
  */
 package org.truffleruby.language.objects;
 
-import com.oracle.truffle.api.dsl.ReportPolymorphism;
 import org.truffleruby.RubyContext;
 import org.truffleruby.RubyLanguage;
 import org.truffleruby.core.klass.RubyClass;
@@ -24,7 +23,6 @@
 import com.oracle.truffle.api.dsl.GenerateUncached;
 import com.oracle.truffle.api.dsl.Specialization;
 
-@ReportPolymorphism
 @GenerateUncached
 public abstract class MetaClassNode extends RubyBaseNode {