Correct some spellings.

Test: mma
Change-Id: Icc49a4ee76f12d302ed18982d334f2f70b7263a8
diff --git a/update_manager/policy.h b/update_manager/policy.h
index b60c4da..05bb2ad 100644
--- a/update_manager/policy.h
+++ b/update_manager/policy.h
@@ -118,7 +118,7 @@
 
   // Information pertaining to update scattering.
   //
-  // The currently knwon (persisted) scattering wallclock-based wait period and
+  // The currently known (persisted) scattering wallclock-based wait period and
   // update check threshold; zero if none.
   base::TimeDelta scatter_wait_period;
   int scatter_check_threshold;