Flatten thread: localize missing string

Bug: twpowertools:157
Change-Id: Iee619a271bf5ef85531071cfdad17d766fe5e8ab
diff --git a/src/lit-locales/source/es.xlf b/src/lit-locales/source/es.xlf
index fd07314..2ee376d 100644
--- a/src/lit-locales/source/es.xlf
+++ b/src/lit-locales/source/es.xlf
@@ -17,6 +17,9 @@
         <target>Más</target>
         <note from="lit-localize">Button to expand the quote message (used in the flatten threads feature).</note>
       </trans-unit>
+<trans-unit id="s6b0ed0c74667d28c">
+  <source><x id="0" equiv-text="${authorName}"/> said:</source>
+</trans-unit>
     </body>
   </file>
 </xliff>