test-link: test bond with use_carrier=1

`use_carrier` is removed from kernel since 6.18 [1], and returns
the following error if set to 0:
> option obsolete, use_carrier cannot be disabled

This causes a failure of test-link-linux, so let's set it to 1.

[1] https://lore.kernel.org/all/2029487.1756512517@famine/

src/core/platform/tests/test-link.c

@@ -124,6 +124,7 @@ software_add(NMLinkType link_type, const char *name)
         int      r;
         const NMPlatformLnkBond nm_platform_lnk_bond_default = {
             .mode        = nmtst_rand_select(3, 1),
+            .use_carrier = 1,
         };
 
         r = nm_platform_link_bond_add(NM_PLATFORM_GET, name, &nm_platform_lnk_bond_default, NULL);