Fix action's description for smart text selection.

Smart text selection was originally implemented to be accessed via
context menu and so the UMA description reflected that. After that it
was decided the feature should also be accessible via touchscreen and so
this CL reflects that update.

Bug: None
Change-Id: Ib4216e7e913d4a7aa2273b23f7e010ff6e883840
Reviewed-on: https://chromium-review.googlesource.com/c/1489792
Auto-Submit: David Jacobo <djacobo@chromium.org>
Commit-Queue: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635693}

tools/metrics/actions/actions.xml

@@ -2221,8 +2221,8 @@ should be able to be added at any place in this file.
   <owner>jorgegil@google.com</owner>
   <description>
     Recorded when a request to the ARC++ container to generate Smart Text
-    Selection actions is made. This happens when the user opens the Context Menu
-    via a right-click.
+    Selection actions is made. This happens both when the user opens the Context
+    Menu via a right-click and by selecting text via touchscreen.
   </description>
 </action>