README.md: fix linked file name [ci skip]
README.md: fix linked file name, COPYING does not a suffix. [Fix GH-1265]
README.ja.md: update a link too.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53950 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
README.md: fix linked file name [ci skip]
README.md: fix linked file name, COPYING does not a suffix.
[Fix GH-1265]
README.ja.md: update a link too.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53950 b2dd03c8-39d4-4d8f-98ff-823fe69b080e