rsa-doc: fix typo

"d_i in RFC8017" -> "d_i" in RFC8017

Reviewed-by: Todd Short <todd.short@me.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from #22868)

(cherry picked from commit c89b553)

doc/man7/EVP_PKEY-RSA.pod

@@ -80,7 +80,7 @@ Up to eight additional "r_i" prime factors are supported.
 =item "rsa-exponent10" (B<OSSL_PKEY_PARAM_RSA_EXPONENT10>) <unsigned integer>
 
 RSA CRT (Chinese Remainder Theorem) exponents. The exponents are known
-as "dP", "dQ" and "d_i in RFC8017".
+as "dP", "dQ" and "d_i" in RFC8017.
 Up to eight additional "d_i" exponents are supported.
 
 =item "rsa-coefficient1" (B<OSSL_PKEY_PARAM_RSA_COEFFICIENT1>) <unsigned integer>