docs/ja_JP/SubmittingPatches: Remove stale maintainer info

Having a stale e-mail address of an unreachable maintainer does
not help in any regard.
Remove said info in the header comment area.
Add note on the translators' credits which has existed since
this file was mainlined.

Signed-off-by: Akira Yokosawa <[email protected]>

Documentation/translations/ja_JP/SubmittingPatches

@@ -1,17 +1,20 @@
 NOTE:
 This is a version of Documentation/process/submitting-patches.rst into Japanese.
-This document is maintained by Keiichi KII <[email protected]>
-and the JF Project team <http://www.linux.or.jp/JF/>.
 If you find any difference between this document and the original file
 or a problem with the translation,
-please contact the maintainer of this file or JF project.
+please contact the maintainer of this file.
 
 Please also note that the purpose of this file is to be easier to read
 for non English (read: Japanese) speakers and is not intended as a
 fork. So if you have any comments or updates of this file, please try
 to update the original English file first.
 
-Last Updated: 2011/06/09
+Comment block below is the exact copy of the note on the translation
+effort at the time of mainlining.  For updates since then, please refer
+to the repository history.
+
+(下のコメントはこれがメインライン化された時点の翻訳活動の記録です。
+それ以降の更新については、リポジトリの履歴を参照してください。)
 
 ==================================
 これは、