Fix use of obsolete flag -o to -r

[email protected]
BUG=
TEST=

Review URL: http://codereview.chromium.org/7966018

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@102354 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/my_reviews.py b/my_reviews.py
index 43e812c..3e1ab73 100755
--- a/my_reviews.py
+++ b/my_reviews.py
@@ -6,7 +6,7 @@
 """Get rietveld stats about the review you done, or forgot to do.
 
 Example:
-  - my_reviews.py -o [email protected] -Q  for stats for last quarter.
+  - my_reviews.py -r [email protected] -Q  for stats for last quarter.
 """
 import datetime
 import optparse