Revert "Note that EVP_CIPHER_get_iv_length returns negative values on…

… error"

This reverts commit 2a6275f.

Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
(Merged from #18946)

doc/man3/EVP_EncryptInit.pod

@@ -1216,7 +1216,7 @@ length.
 EVP_CIPHER_CTX_set_padding() always returns 1.
 
 EVP_CIPHER_get_iv_length() and EVP_CIPHER_CTX_get_iv_length() return the IV
-length, zero if the cipher does not use an IV and a negative value on error.
+length or zero if the cipher does not use an IV.
 
 EVP_CIPHER_CTX_get_tag_length() return the tag length or zero if the cipher
 does not use a tag.