branch --set-upstream-to: be consistent when advising

branch --set-upstream-to: be consistent when advising

"git branch --set-upstream-to" behaves differently when advice is
enabled/disabled:

|                 | error prefix | exit code |
|-----------------+--------------+-----------|
| advice enabled  | error:       |         1 |
| advice disabled | fatal:       |       128 |

Make both cases consistent by using die_message() when advice is
enabled (this was first proposed in [1]).

[1] https://lore.kernel.org/git/211210.86ee6ldwlc.gmgdl@evledraar.gmail.com

Signed-off-by: Glen Choo <redacted>
Signed-off-by: Junio C Hamano <redacted>