t/pack-refs-tests: move the 'test_done' to callees

In ac0bad0af4 (t0601: refactor tests to be shareable, 2025-09-19), we
refactored 't/t0601-reffiles-pack-refs.sh' to move all of the tests to
't/pack-refs-tests.sh', which became a common test suite which was also
used by 't/t1463-refs-optimize.sh'.

This also moved the 'test_done' directive to 't/pack-refs-tests.sh'.
Which inhibits additional tests from being added to either of the tests.
Let's move the directive out to both the tests, so that we can add
additional specific tests to them. Also the test flow logic shouldn't be
part of tests which can be embedded in other test scripts.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/t/pack-refs-tests.sh b/t/pack-refs-tests.sh
index 095823d..81086c3 100644
--- a/t/pack-refs-tests.sh
+++ b/t/pack-refs-tests.sh
@@ -459,5 +459,3 @@
 		test_grep ! "^\^" .git/packed-refs
 	)
 '
-
-test_done
diff --git a/t/t0601-reffiles-pack-refs.sh b/t/t0601-reffiles-pack-refs.sh
index 12cf5d1..3c70697 100755
--- a/t/t0601-reffiles-pack-refs.sh
+++ b/t/t0601-reffiles-pack-refs.sh
@@ -18,3 +18,5 @@
 . ./test-lib.sh
 
 . "$TEST_DIRECTORY"/pack-refs-tests.sh
+
+test_done
diff --git a/t/t1463-refs-optimize.sh b/t/t1463-refs-optimize.sh
index c11c905..9afe3c1 100755
--- a/t/t1463-refs-optimize.sh
+++ b/t/t1463-refs-optimize.sh
@@ -15,3 +15,5 @@
 
 pack_refs='refs optimize'
 . "$TEST_DIRECTORY"/pack-refs-tests.sh
+
+test_done