Fix typo wording in documentation

Change-Id: I905ab638a4a884759966e491f091961377e91f15
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/lib/event_notification.py b/lib/event_notification.py
index dac6c5e..1e12bbc 100755
--- a/lib/event_notification.py
+++ b/lib/event_notification.py
@@ -70,7 +70,7 @@
               [Value]:               23813
 
         Description of argument(s):
-        dbus_path              The subcribing event's path (e.g.
+        dbus_path              The subscribing event's path (e.g.
                                "/xyz/openbmc_project/sensors").
         enable_trace           Enable or disable trace.
         """