[GHC] #13590: Update Cabal submodule to whatever the final Cabal 2.0 release is

[GHC]

#13590: Update Cabal submodule to whatever the final Cabal 2.0 release is
-------------------------------------+-------------------------------------
        Reporter:  ezyang            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.1
       Component:  libraries         |              Version:  8.2.1-rc2
  (other)                            |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by refold):

 `Cabal-v2.0.0.0` tag has been created.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13590#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler