Documentation: trace/stm: drop doubled words

Change "and and" to "and an".
Fix spello of "example".
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Link: https://lore.kernel.org/r/20200703212453.30553-4-rdunlap@infradead.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/trace/stm.rst

@@ -33,8 +33,8 @@ This policy is a tree structure containing rules (policy_node) that
 have a name (string identifier) and a range of masters and channels
 associated with it, located in "stp-policy" subsystem directory in
 configfs. The topmost directory's name (the policy) is formatted as
-the STM device name to which this policy applies and and arbitrary
-string identifier separated by a stop. From the examle above, a rule
+the STM device name to which this policy applies and an arbitrary
+string identifier separated by a stop. From the example above, a rule
 may look like this::
 
 	$ ls /config/stp-policy/dummy_stm.my-policy/user