incorrect rndc key match

Hi,

there is a bug in https://gitlab.isc.org/isc-projects/stork/-/blob/master/backend/agent/bind9.go#L132

the keyword of key block is key,

	key "name" {
		algorithm "hmac-sha256";
		secret "OmItW1lOyLVUEuvv+Fme+Q==";
	};

but the regex matches keys.