Restore comment in ssl-opt.sh as it is still relevent

Signed-off-by: Ben Taylor <ben.taylor@linaro.org>
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 0cf9e23..ef78ef0 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -9443,6 +9443,15 @@
             -C "mbedtls_ecdh_make_public.*\(4b00\|-248\)" \
             -C "mbedtls_pk_sign.*\(4b00\|-248\)"
 
+# The following test cases for restartable ECDH come in two variants:
+# * The "(USE_PSA)" variant expects the current behavior, which is the behavior
+#   from Mbed TLS 3.x when MBEDTLS_USE_PSA_CRYPTO is disabled. This tests
+#   the partial implementation where ECDH in TLS is not actually restartable.
+# * The "(no USE_PSA)" variant expects the desired behavior. These test
+#   cases cannot currently pass because the implementation of restartable ECC
+#   in TLS is partial: ECDH is not actually restartable. This is the behavior
+#   from Mbed TLS 3.x when MBEDTLS_USE_PSA_CRYPTO is enabled.
+#
 # As part of resolving https://github.com/Mbed-TLS/mbedtls/issues/7294,
 # we will remove the "(USE_PSA)" test cases and run the "(no USE_PSA)" test
 # cases.