Fix inaccuracy in key exchange summary

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/docs/use-psa-crypto.md b/docs/use-psa-crypto.md
index c8f89d0..6300bf0 100644
--- a/docs/use-psa-crypto.md
+++ b/docs/use-psa-crypto.md
@@ -160,7 +160,7 @@
   - ECDHE computation client-side
   - ECDSA verification both sides
   - ECDSA signature (if using `mbedtls_pk_setup_opaque()`)
-- PSK: client-side PSA-held using `mbedtls_ssl_conf_psk_opaque()`
+- PSK: PSA-held keys using `mbedtls_ssl_conf_psk_opaque()`
 - DHE-PSK: not covered
 - RSA-PSK: not covered
 - ECDHE-PSK: not covered