t7300: add a missing SYMLINKS prerequisite

The test fails on Windows since 2dec68c (tests: add missing &&, batch 2).

Even though this test allocates and leaves behind files, subsequent tests
do not depend on this, so it is safe to just skip it.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7300-clean.sh

@@ -179,7 +179,7 @@ test_expect_success 'git clean -d with prefix and path' '
 
 '
 
-test_expect_success 'git clean symbolic link' '
+test_expect_success SYMLINKS 'git clean symbolic link' '
 
 	mkdir -p build docs &&
 	touch a.out src/part3.c docs/manual.txt obj.o build/lib.so &&