cros: A string change requested by TC for KSV.

This cl changes one string in Keyboard Shortcut Helper to make it
more clear to the users.

Bug: b/74186947
Test: manually tested.
Change-Id: I4af4d7a99c9a279a775309e58584c06e63f7a136
Reviewed-on: https://chromium-review.googlesource.com/964586Reviewed-by: Tao Wu <wutao@chromium.org>
Reviewed-by: Qiang Xu <warx@google.com>
Commit-Queue: Tao Wu <wutao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543454}

ash/components/shortcut_viewer_strings.grdp

@@ -112,7 +112,7 @@
     Press and hold <ph name="alt">$1<ex>Alt</ex></ph>, tap <ph name="tab">$2<ex>v</ex></ph> until you get to the window you want to open, then release.
   </message>
   <message name="IDS_KSV_DESCRIPTION_CYCLE_BACKWARD_MRU" desc="Description of the command in keyboard shortcut viewer.">
-    Open the window you used least recently
+    Open the window that has been unused for the longest time
   </message>
   <message name="IDS_KSV_SHORTCUT_CYCLE_BACKWARD_MRU" desc="Human readable version of the keyboard shortcut.">
     Press and hold <ph name="alt">$1<ex>Alt</ex></ph><ph name="separator">$2<ex>+</ex></ph><ph name="shift">$3<ex>Shift</ex></ph>, tap <ph name="tab">$4<ex>v</ex></ph> until you get to the window you want to open, then release.