rule: don't print trailing statement whitespace

rule: don't print trailing statement whitespace

This trailing whitespace is annoying when working with the textual output
of nft.

Before:

table t {
	chain c {
		ct state new
			    ^
	}
}

After:

table t {
	chain c {
		ct state new
	}
}

Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>