[GHC] #15406: Fix a small typo in TcType.hs

[GHC]

#15406: Fix a small typo in TcType.hs
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        Reporter:  v0d1ch            |                Owner:  v0d1ch
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Documentation     |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4976
       Wiki Page:                    |
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Changes (by v0d1ch):

 * status:  new => patch
 * differential:   => Phab:D4976


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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15406#comment:2>
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