pk: update documentation of mbedtls_pk_setup_opaque() based on #8951

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index 60942d7e..3b9d18d 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -377,9 +377,8 @@
  *                      * sign, sign_ext: try #PSA_ALG_DETERMINISTIC_ECDSA()
  *                        first and, in case it fails, try with #PSA_ALG_ECDSA().
  *                  * RSA:
- *                      * sign: #PSA_ALG_RSA_PKCS1V15_SIGN();
- *                      * sign_ext: use the algorithm associated with the wrapped
- *                        PSA key;
+ *                      * sign, sign_ext: use the algorithm associated with the
+ *                        wrapped PSA key;
  *                      * verify: not supported;
  *                      * verify_ext: not supported;
  *                      * decrypt: #PSA_ALG_RSA_PKCS1V15_CRYPT;