Revert lost translations in es, gl, ja

Looks like Jacques needs to enable these locales on his system.

docs/ja_JP.UTF-8/html/FAQ.html

@@ -17,15 +17,15 @@
             width="205"
             height="210"
             alt="Tux Paint"><br>
-        version 0.9.27        Frequently Asked Questions      </h1>
+        バージョン 0.9.27        Frequently Asked Questions      </h1>
 
       <p>
-        Copyright &copy; 2002-2021 by various contributors; see AUTHORS.<br>
+        Copyright &copy; 2002-2021 by various contributors; "AUTHORS" 参照.<br>
         <a href="http://www.tuxpaint.org/">http://www.tuxpaint.org/</a>
       </p>
 
       <p>
-        August 29, 2021      </p>
+        2021年8月29日      </p>
     </center>
 
     <hr size="2"
@@ -34,10 +34,10 @@
     <table border="2"
            cellspacing="0"
            cellpadding="2"
-           summary="Table of Contents">
+           summary="目次">
       <tr>
         <th>
-          Table of Contents        </th>
+          目次        </th>
       </tr>
 
       <tr>