Log Message:
Update to 2.3.0

Upstream changes:
R6 2.3.0

    Vignettes are no longer included as part of the source package because of \ 
their large size. Documentation is now at https://r6.r-lib.org/.

    Fixed #125: The print.R6 method now always returns the object that was \ 
passed to it.

    Fixed #155: In some cases, a cloned object’s methods could refer to the \ 
wrong super object. (#156)

    Fixed #94, #133: When cloning an object which contained a function that is \ 
not a method, the corresponding function in the new object would have its \ 
environment changed, as though it were a method. Now it no longer has a changed \ 
environment. (#156)

    Fixed #121: If a finalize method was present, it would prevent objects \ 
passed to initialize from getting GC’d.

    Fixed #158: If a $set method of an R6 generator object is given the value \ 
NULL, it previously removed the named item. Now it adds the named item with the \ 
value NULL.

    Fixed #159: Printing an R6 object containing a large vector was slow.