Deactivate and remove the active_block_parser from the all_block_parsers list

Property definitions

markdown2 $ MdParser :: remove_active_block_parser
	# Deactivate and remove the `active_block_parser` from the `all_block_parsers` list
	private fun remove_active_block_parser do
		var old = active_block_parser
		deactivate_block_parser
		all_block_parsers.remove(old)
		old.block.unlink
	end
lib/markdown2/markdown_block_parsing.nit:73,2--79,4