lib/crypto: poly1305: Remove unused function poly1305_is_arch_optimized()

poly1305_is_arch_optimized() is unused, so remove it.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250829152513.92459-2-ebiggers@kernel.org


Signed-off-by: Eric Biggers <ebiggers@kernel.org>