[iOS] Fix a typo in ios_strings_resources.grd

ios/chrome/app/strings/ios_strings_resources.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <!--
 This file contains definition of resources that will be translated for each
 locale.  The variables is_win, is_macosx, is_linux, is_ios and is_posix are
 available for making strings OS specific.  Other platform defines such as
 use_titlecase are declared in build/common.gypi.
 
 The strings in that file are specific to iOS, thus is_ios will be true and
 all other OS specific variables will be false.
 -->
 
 <grit base_dir="." latest_public_release="0" current_release="1"
       source_lang_id="en" enc_check="möl">
   <outputs>
     <output filename="grit/ios_strings_resources.h" type="rc_header">
-      <emit emit_type="preprend"></emit>
+      <emit emit_type="prepend"></emit>
     </output>
     <output filename="ios_strings_resources_am.pak" type="data_package" lang="am" />
     <output filename="ios_strings_resources_ar.pak" type="data_package" lang="ar" />
     <if expr="pp_ifdef('use_third_party_translations')">
       <output filename="ios_strings_resources_ast.pak" type="data_package" lang="ast" />
     </if>
     <output filename="ios_strings_resources_bg.pak" type="data_package" lang="bg" />
     <output filename="ios_strings_resources_bn.pak" type="data_package" lang="bn" />
     <if expr="pp_ifdef('use_third_party_translations')">
       <output filename="ios_strings_resources_bs.pak" type="data_package" lang="bs" />
@@ skipping 147 matching lines @@
     <file path="resources/ios_strings_resources_zh-TW.xtb" lang="zh-TW" />
   </translations>
   <release seq="1" allow_pseudo="false">
     <messages fallback_to_english="true">
       <message name="IDS_IOS_VERSION_COPIED" desc="The message displayed when the version label is tapped (in About settings) [Length: 10em] [iOS only]">
         Copied
       </message>
     </messages>
   </release>
 </grit>