Use `*` instead of `**` in .editorconfig

It seems `**` is same as `*` when no `/` exist.
[ci skip]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59609 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

.editorconfig

@@ -8,10 +8,10 @@ tab_width = 8
 indent_style = tab
 indent_size = 4
 
-[**.bat]
+[*.bat]
 end_of_line = crlf
 
-[**.rb]
+[*.rb]
 indent_style = space
 indent_size = 2