test: add a comment specifying why restartable cannot be tested

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index e459fc7..2b789c3 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -2108,6 +2108,9 @@
     # TODO: make these work - #6862
     scripts/config.py unset MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED
     scripts/config.py unset MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA_ENABLED
+    # Restartable feature is not yet supported by PSA. Once it will in
+    # the future, the following line could be removed (see issues
+    # 6061, 6332 and following ones)
     scripts/config.py unset MBEDTLS_ECP_RESTARTABLE
 }