Update help message dump-timing -> dump-timings.

Test: m
Change-Id: I14fd14db7cad267cef42abab058de83bf0fcb980
diff --git a/dex2oat/dex2oat.cc b/dex2oat/dex2oat.cc
index 27bec1d..a70e551 100644
--- a/dex2oat/dex2oat.cc
+++ b/dex2oat/dex2oat.cc
@@ -345,7 +345,7 @@
              CompilerOptions::kDefaultInlineMaxCodeUnits);
   UsageError("      Default: %d", CompilerOptions::kDefaultInlineMaxCodeUnits);
   UsageError("");
-  UsageError("  --dump-timing: display a breakdown of where time was spent");
+  UsageError("  --dump-timings: display a breakdown of where time was spent");
   UsageError("");
   UsageError("  -g");
   UsageError("  --generate-debug-info: Generate debug information for native debugging,");