Increase length of "Suppress Dialogs" string to 25em.

BUG=669589

Review-Url: https://codereview.chromium.org/2546063003
Cr-Commit-Position: refs/heads/master@{#436293}

ios/chrome/app/strings/ios_strings.grd

@@ -709,7 +709,7 @@ To adjust your search term, long press to select. To refine your search, slide t
       <message name="IDS_IOS_ICON_SEARCH" desc="Accessibility label for the search icon [iOS only].">
         Search
       </message>
-      <message name="IDS_IOS_JAVA_SCRIPT_DIALOG_BLOCKING_BUTTON_TEXT" desc="The text used for the button added to JavaScript dialogs to prevent a page from spamming the user with endless alerts. [Length:20em]">
+      <message name="IDS_IOS_JAVA_SCRIPT_DIALOG_BLOCKING_BUTTON_TEXT" desc="The text used for the button added to JavaScript dialogs to prevent a page from spamming the user with endless alerts. [Length:25em]">
         Suppress Dialogs
       </message>
       <message name="IDS_IOS_KEYBOARD_BOOKMARK_THIS_PAGE" desc="In Title Case: Title of the keyboard shortcut that bookmarks the current page. [Length: 20 em] [iOS only]">