pk: improve description for the next opaque ID field

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index dae61da..8d6d60f 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -236,7 +236,7 @@
  * \brief           Public key container
  *
  * \note            The priv_id is guarded by MBEDTLS_PSA_CRYPTO_C and not
- *                  only by MBEDTLS_USE_PSA_CRYPTO because it can be used also
+ *                  by MBEDTLS_USE_PSA_CRYPTO because it can be used also
  *                  in mbedtls_pk_sign_ext for RSA keys.
  */
 typedef struct mbedtls_pk_context {