tg-info: fix sed typo

tg-info: fix sed typo

There was a semicolon missing before a closing brace.  The result
is an error message on some operating systems (e.g., Mac OS 10.3).

	$ tg info
	Topic Branch: t/some-topic (       2/       2 commits)
	Subject: [PATCH] t/some-topic
	Base: 082a7c9
	sed: 1: "1{s/^/Depends: /;n}; s/ ...": extra characters a
	t the end of n command

Signed-off-by: Jonathan Nieder <jrnieder@uchicago.edu>