Revert lost translations in es, gl, ja

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

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

@@ -17,16 +17,16 @@
             width="205"
             height="210"
             alt="Tux Paint"><br>
-        version 0.9.27<br/>
+        バージョン 0.9.27<br/>
         Signals Documentation      </h1>
 
       <p>
-        Copyright &copy; 2019-2021 by various contributors; see AUTHORS.<br>
+        Copyright &copy; 2019-2021 by various contributors; "AUTHORS" 参照.<br>
         <a href="http://www.tuxpaint.org/">http://www.tuxpaint.org/</a>
       </p>
 
       <p>
-        March  9, 2021      </p>
+        2021年3月 9日      </p>
     </center>
 
     <hr>
@@ -50,7 +50,7 @@
           <b>Note:</b> From other parts of the interface, the signal is currently interpreted as a request to go back (e.g., from the "New" dialog back to the main interface), as if a "Back" button in Tux Paint were clicked, or the <b><code>[Esc]</code></b> was key pressed.        </p>
 
         <p>
-          Example: <code>killall tuxpaint</code>        </p>
+          例：<code>killall tuxpaint</code>        </p>
       </dd>
 
       <dt>
@@ -68,7 +68,7 @@
           <b>Note:</b> From other parts of the interface, unfortunately, Tux Paint will go back one level in the interface.  Therefore, at this time, it may be necessary to send this signal to Tux Paint a few times, for it to quit completely.        </p>
 
         <p>
-          Example: <code>killall -s SIGUSR1 tuxpaint</code>        </p>
+          例：<code>killall -s SIGUSR1 tuxpaint</code>        </p>
       </dd>
     </dl>
   </body>