[Mfill Android] State location of suggestions in announcement

After some discussion, we decided to add the "above the keyboard" line
to the opening announcement, see linked bug for details.

Screenshots don't need to be updated since they can't show the string
anyway (as it's only heard via talkback).

Bug: 1009140
Change-Id: Iddd74a87bf67fc679b341505e0d585dc8dd5dc63
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1865217Reviewed-by: Ioana Pandele <ioanap@chromium.org>
Commit-Queue: Friedrich [CET] <fhorschig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706841}

chrome/android/features/keyboard_accessory/internal/java/strings/android_keyboard_accessory_strings.grd

@@ -107,7 +107,7 @@
         Passwords available
       </message>
       <message name="IDS_AUTOFILL_KEYBOARD_ACCESSORY_MODERN_CONTENT_DESCRIPTION" desc="The text announced by the screen reader when the autofill suggestions and fallbacks are shown.">
-        Autofill suggestions available
+        Autofill suggestions available above the keyboard
       </message>
       <message name="IDS_KEYBOARD_ACCESSORY_SHEET_HIDE" desc="Description for the active icon button that closes an accessory sheet and brings back the keyboard.">
           Show keyboard