Update strings for the magnifiers shortcuts in KSH

Based on UX feedback.

BUG=848070

Change-Id: I794b8069d74379887ad5ad04070873eb8aeaaf94
Reviewed-on: https://chromium-review.googlesource.com/1080170Reviewed-by: Tao Wu <wutao@chromium.org>
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563064}

ash/components/shortcut_viewer_strings.grdp

@@ -97,10 +97,10 @@
 
   <!-- Shortcuts descriptions -->
   <message name="IDS_KSV_DESCRIPTION_TOGGLE_DOCKED_MAGNIFIER" desc="Description of the command in keyboard shortcut viewer.">
-    Toggle the Docked Magnifier on or off
+    Turn the docked magnifier on or off
   </message>
   <message name="IDS_KSV_DESCRIPTION_TOGGLE_FULLSCREEN_MAGNIFIER" desc="Description of the command in keyboard shortcut viewer.">
-    Toggle the Fullscreen Magnifier on or off
+    Turn the fullscreen magnifier on or off
   </message>
   <message name="IDS_KSV_DESCRIPTION_LOCK_SCREEN" desc="Description of the command in keyboard shortcut viewer.">
     Lock screen