tests: rename a test having to do with shallow submodules

Rename the t5614-clone-submodules.sh test to
t5614-clone-submodules-shallow.sh. It's not a general test of
submodules, but of shallow cloning in relation to submodules. Move it
to create another similar t56*-clone-submodules-*.sh test.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/t5614-clone-submodules.sh b/t/t5614-clone-submodules-shallow.sh
similarity index 100%
rename from t/t5614-clone-submodules.sh
rename to t/t5614-clone-submodules-shallow.sh