fix(editorconfig): a custom property is treated as a section (#34445)

Problem: A custom property containing a pair of square brackets will be
treated as a section.
Solution: Change the logic parsing a section, remove the first match
regex `%b[]`.

Signed-off-by: fortime <palfortime@gmail.com>

runtime/lua/editorconfig.lua

@@ -241,7 +241,7 @@ local function parse_line(line)
   end
 
   --- @type string?
-  local glob = (line:match('%b[]') or ''):match('^%s*%[(.*)%]%s*$')
+  local glob = line:match('^%s*%[(.*)%]%s*$')
   if glob then
     return glob
   end