Fix typo errors in devstack documentation

This submission fixes typo errors in following files
  1. contributing.rst
  2. exerciserc.rst
  3. faq.rst
  4. local.conf.rst
  5. openrc.rst

Change-Id: I2b2d61673c3c95f60c56978b5a81016603fef252
diff --git a/doc/source/exerciserc.rst b/doc/source/exerciserc.rst
index f3780c3..dacae2e 100644
--- a/doc/source/exerciserc.rst
+++ b/doc/source/exerciserc.rst
@@ -3,7 +3,7 @@
 ==============================
 
 ``exerciserc`` is used to configure settings for the exercise scripts.
-The values shown below are the default values. Thse can all be
+The values shown below are the default values. These can all be
 overridden by setting them in the ``localrc`` section.
 
 ACTIVE\_TIMEOUT