Parsing: allow primary ctor in object syntactically

It's needed for better recovering for cases of changes like 'class' -> 'object'

The only sensible case when it's may be bad:
class A {
   object B
   constructor() : super()
}

But it seems to be rare, and ';' can be used to separate object from secondary ctor

compiler/testData/psi/annotation/at/validDeclarations.kt

@@ -28,7 +28,7 @@ private @open [Ann1(1)] @Ann2("1") Ann3("2") class A(
 
     @companion object
 
-    @companion @private object B
+    @companion @private object B;
 
     @main