Revert "xsk: Document ability to redirect to any socket bound to the same umem"

This reverts commit 968595a9

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Reported-by: Yuval El-Hanany <YuvalE@radware.com>
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/xdp-newbies/8100DBDC-0B7C-49DB-9995-6027F6E63147@radware.com
Link: https://lore.kernel.org/bpf/20240604122927.29080-3-magnus.karlsson@gmail.com