t6302: simplify non-gpg cases

t6302: simplify non-gpg cases

When commit 618310a taught t6302 to run without the GPG
prerequisite, it did so by conditionally creating the signed
tags only when gpg is available. As a result, further tests
need to take this into account, which they can do with the
test_prepare_expect helper. This is a minor hassle, though,
as the helper cannot easily cover all cases (it just matches
"signed" in the output, so all output must include the
actual refname).

Instead, let's take a different approach. We'll always
create the tags, and only conditionally sign them. This does
mean our tag-names are a minor lie, but it lets the tests
which do not care about signing easily behave the same in
all settings. We'll include a comment to document our lie
and avoid confusing further test-writers.

Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>