Revert "Avoid get class when the object is python class"

This reverts commit 8d7c757.

This change was breaking pytorch and there is nothing in CPython source
that would support its existence. I wasn't able to find what it was
attempting to fix. Whatever it was, it needs to be fixed in a different
way.

Author: msimacek

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/argument/CreateArgumentsNode.java

@@ -56,7 +56,6 @@
 import com.oracle.graal.python.builtins.objects.module.PythonModule;
 import com.oracle.graal.python.builtins.objects.object.PythonObject;
 import com.oracle.graal.python.builtins.objects.str.PString;
-import com.oracle.graal.python.builtins.objects.type.PythonClass;
 import com.oracle.graal.python.nodes.ErrorMessages;
 import com.oracle.graal.python.nodes.PGuards;
 import com.oracle.graal.python.nodes.PNodeWithContext;
@@ -478,8 +477,7 @@ static void doEnclosingTypeCheck(@SuppressWarnings("unused") Signature signature
                         @Cached GetClassNode getClassNode,
                         @Cached IsSubtypeNode isSubtypeMRONode,
                         @Cached PRaiseNode raiseNode) {
-            Object derived = self instanceof PythonClass ? self : getClassNode.execute(self);
-            if (!isSubtypeMRONode.execute(derived, callable.getEnclosingType())) {
+            if (!isSubtypeMRONode.execute(getClassNode.execute(self), callable.getEnclosingType())) {
                 CompilerDirectives.transferToInterpreterAndInvalidate();
                 throw raiseNode.raise(PythonBuiltinClassType.TypeError, "descriptor '%s' for '%p' objects doesn't apply to a '%p' object",
                                 callable.getName(), callable.getEnclosingType(), self);