m68k: defconfig: Update defconfigs for v6.2-rc3

  - Drop CONFIG_NFT_OBJREF=m (removed in commit d037abc2
    ("netfilter: nft_objref: make it builtin")),
  - Drop CONFIG_TEST_STRSCPY=m (replaced by auto-modular
    CONFIG_STRSCPY_KUNIT_TEST in commit 41eefc46 ("string:
    Convert strscpy() self-test to KUnit")),
  - Drop CONFIG_TEST_SIPHASH=m (replaced by auto-modular
    CONFIG_SIPHASH_KUNIT_TEST in commit fb3d88ab

 ("siphash:
    Convert selftest to KUnit")).

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/fdd3b827ebc5abea6c295df4121048a6a03b698a.1672654705.git.geert@linux-m68k.org
Link: https://lore.kernel.org/r/6c4589bc56ffba0f923a7361262397f6c32a3dc1.1673255008.git.geert@linux-m68k.org