Remove superfluous use of boxing in ObjectStreamClass

Some of these seem superfluous, or possible misguided.

$ grep valueOf src/java.base/share/classes/java/io/ObjectStreamClass.java
                        suid = Long.valueOf(0);
            suid = Long.valueOf(0);
        suid = Long.valueOf(0);
        long suid = Long.valueOf(model.getSerialVersionUID());
        suid = Long.valueOf(in.readLong());
                return Long.valueOf(f.getLong(null));