Remove doubled words

Reviewers: bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie, carter

Differential Revision: https://phabricator.haskell.org/D4368

docs/users_guide/8.2.1-notes.rst

@@ -154,7 +154,7 @@ Compiler
   directive on undefined identifiers.
 
 - GHC will no longer automatically infer the kind of higher-rank type synonyms;
-  you must explicitly explicitly annotate the synonym with a kind signature.
+  you must explicitly annotate the synonym with a kind signature.
   For example, given::
 
     data T :: (forall k. k -> Type) -> Type

docs/users_guide/phases.rst

@@ -900,9 +900,8 @@ for example).
     The threaded runtime system provides the following benefits:
 
     -  It enables the :rts-flag:`-N ⟨x⟩` RTS option to be used,
-       which allows threads to run in parallelparallelism on a
-       multiprocessormultiprocessorSMP or multicoremulticore machine.
-       See :ref:`using-smp`.
+       which allows threads to run in parallel on a multiprocessor 
+       or multicore machine. See :ref:`using-smp`.
 
     -  If a thread makes a foreign call (and the call is not marked
        ``unsafe``), then other Haskell threads in the program will