Generating generic signatures in the presence of `AnyVal` is wrong

[hamzaremmal]

Compiler version

ce57b71

Minimized code

class Box[A](v: A) extends AnyVal
class Foo:
    def box[A]: Box[A] = ???

Output

//> javap Foo  
Compiled from "test.scala"
public class Foo {
  public Foo();
  public <A> java.lang.Object box();
}

Expectation

//> javap Foo
Compiled from "test.scala"
public class Foo {
  public <A> A box();
  public Foo();
}

Notes

First mentioned in #22140 (should be the same fix)