t5606: run clone branch name test with protocol v2

4f37d45706 ("clone: respect remote unborn HEAD", 2021-02-05) introduces
a new feature (if the remote has an unborn HEAD, e.g. when the remote
repository is empty, use it as the name of the branch) that only works
in protocol v2, but did not ensure that one of its tests always uses
protocol v2, and thus that test would fail if
GIT_TEST_PROTOCOL_VERSION=0 (or 1) is used. Therefore, add "-c
protocol.version=2" to the appropriate test.

(The rest of the tests from that commit have "-c protocol.version=2"
already added.)

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5606-clone-options.sh

@@ -106,7 +106,7 @@ test_expect_success 'chooses correct default initial branch name' '
 	git -c init.defaultBranch=foo init --bare empty &&
 	test_config -C empty lsrefs.unborn advertise &&
 	GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME= \
-	git -c init.defaultBranch=up clone empty whats-up &&
+	git -c init.defaultBranch=up -c protocol.version=2 clone empty whats-up &&
 	test refs/heads/foo = $(git -C whats-up symbolic-ref HEAD) &&
 	test refs/heads/foo = $(git -C whats-up config branch.foo.merge)
 '