Fix incorrect adb shell cmd help command for pull-source

Test: statsd should pass, but it's not required as it's just an update
in help instruction.

Change-Id: I36f4e4794ae8066abdeaac98db5e679a3bcf0a06
diff --git a/cmds/statsd/src/StatsService.cpp b/cmds/statsd/src/StatsService.cpp
index 747a571..61171f9 100644
--- a/cmds/statsd/src/StatsService.cpp
+++ b/cmds/statsd/src/StatsService.cpp
@@ -234,7 +234,7 @@
     fprintf(out, "  Removes all configs from disk.\n");
     fprintf(out, "\n");
     fprintf(out, "\n");
-    fprintf(out, "usage: adb shell cmds stats pull-source [int] \n");
+    fprintf(out, "usage: adb shell cmd stats pull-source [int] \n");
     fprintf(out, "\n");
     fprintf(out, "  Prints the output of a pulled metrics source (int indicates source)\n");
     fprintf(out, "\n");