Fix copypasta: signature -> encryption

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/psa/crypto_values.h b/include/psa/crypto_values.h
index baaabff..f0203f4 100644
--- a/include/psa/crypto_values.h
+++ b/include/psa/crypto_values.h
@@ -1259,7 +1259,7 @@
  *                      #PSA_ALG_IS_HASH(\p hash_alg) is true) to use
  *                      for MGF1.
  *
- * \return              The corresponding RSA OAEP signature algorithm.
+ * \return              The corresponding RSA OAEP encryption algorithm.
  * \return              Unspecified if \p hash_alg is not a supported
  *                      hash algorithm.
  */