tests: fix a memory leak in test-oidtree.c

Fix a memory leak in t/helper/test-oidtree.c, we were not freeing the
"struct strbuf" we used for the stdin input we parsed. This leak has
been here ever since 92d8ed8ac1 (oidtree: a crit-bit tree for
odb_loose_cache, 2021-07-07).

Now that it's fixed we can declare that t0069-oidtree.sh will pass
under GIT_TEST_PASSING_SANITIZE_LEAK=true.

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

t/helper/test-oidtree.c

@@ -45,5 +45,8 @@ int cmd__oidtree(int argc, const char **argv)
 			die("unknown command: %s", line.buf);
 		}
 	}
+
+	strbuf_release(&line);
+
 	return 0;
 }

t/t0069-oidtree.sh

@@ -1,6 +1,7 @@
 #!/bin/sh
 
 test_description='basic tests for the oidtree implementation'
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 maxhexsz=$(test_oid hexsz)