[Browsing Data] Remove unused strings in components

components/browsing_data_strings.grdp

 <?xml version="1.0" encoding="utf-8"?>
 <grit-part>
   
   <!-- Clear Browsing Data counters-->
   <message name="IDS_CLEAR_BROWSING_DATA_CALCULATING" desc="A text that is shown while the data volume is being counted.">
     Calculating...
   </message>
-  <message name="IDS_CLEAR_BROWSING_DATA_UNKNOWN_SIZE" desc="A text that is shown when the data volume could not be calculated. This string refers to uncountable objects, such as cache.">
-    unknown size
-  </message>
-  <message name="IDS_CLEAR_BROWSING_DATA_UNKNOWN_AMOUNT" desc="A text that is shown when the data volume could not be calculated. This string refers to countable objects, such as history entries or passwords.">
-    unknown amount
-  </message>
   <message name="IDS_DEL_BROWSING_HISTORY_COUNTER" desc="A counter showing how many items of browsing history the user has.">
     {COUNT, plural,
      =0 {none}
      =1 {1 item}
      other {# items}}
   </message>
   <message name="IDS_DEL_BROWSING_HISTORY_COUNTER_SYNCED" desc="A counter showing the user how many local items of browsing history they have, and informing them that more items might be synced. In the case when COUNT is zero, the counter only mentions existence of synced items.">
     {COUNT, plural,
      =0 {at least 1 item on synced devices}
      =1 {1 item (and more on synced devices)}
@@ skipping 66 matching lines @@
      =1 {and 1 more}
      other {and # more}}
   </message>
   <message name="IDS_DEL_MEDIA_LICENSES_COUNTER_GENERAL_COMMENT" desc="A static message shown in the Clear Browsing Data dialog explaining to the user that clearing media licenses will result in the user being unable to play some premium content">
     You may lose access to premium content from some sites.
   </message>
   <message name="IDS_DEL_MEDIA_LICENSES_COUNTER_SITE_COMMENT" desc="A message shown in the Clear Browsing Data dialog explaining to the user that clearing media licenses will result in the user being unable to play some premium content from at least one specific web site">
      You may lose access to premium content from <ph name="SITE">$1<ex>youtube.com</ex></ph> and some other sites.
   </message>
 </grit-part>