filetypes.lua: Change block comment (#2566)

See: https://www.lua.org/pil/1.3.html

data/filedefs/filetypes.lua

@@ -52,7 +52,7 @@ mime_type=text/x-lua
 comment_single=--
 # multiline comments
 comment_open=--[[
-comment_close=]]--
+comment_close=--]]
 
 # set to false if a comment character/string should start at column 0 of a line, true uses any
 # indentation of the line, e.g. setting to true causes the following on pressing CTRL+d