syntaxes: put the 'linter' and 'formatter' commands on a separate line

To show that they are a different class of thing than the file-matching
regexes and the comment thing, which all kind of "describe" the file.

syntax/lua.nanorc

@@ -5,9 +5,10 @@
 
 syntax lua "\.lua$"
 magic "Lua script"
-linter "luacheck --no-color"
 comment "--"
 
+linter luacheck --no-color
+
 color brightwhite "\[\[.*\]\]"
 
 # Operators