Remove the delimiter delim

Property definitions

markdown2 $ MdInlineParser :: remove_delimiter
	# Remove the delimiter `delim`
	private fun remove_delimiter(delim: nullable MdDelimiter) do
		if delim == null then return

		var prev = delim.prev
		if prev != null then
			prev.next = delim.next
		end
		var next = delim.next
		if next == null then
			# top of stack
			last_delimiter = prev
		else
			next.prev = prev
		end
	end
lib/markdown2/markdown_inline_parsing.nit:1046,2--1061,4