Remove "export_key" from transparent driver json

Transparent drivers don't have this entry points. Other entry points
that are only for opaque drivers are not listed here but only in the
opaque_driver.json file, so this was likely a mistake.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/scripts/data_files/driver_jsons/mbedtls_test_transparent_driver.json b/scripts/data_files/driver_jsons/mbedtls_test_transparent_driver.json
index 9eb259f..b9b2d68 100644
--- a/scripts/data_files/driver_jsons/mbedtls_test_transparent_driver.json
+++ b/scripts/data_files/driver_jsons/mbedtls_test_transparent_driver.json
@@ -7,7 +7,7 @@
         {
             "_comment":     "The Mbed TLS transparent driver supports import key/export key",
             "mbedtls/c_condition":    "defined(PSA_CRYPTO_DRIVER_TEST)",
-            "entry_points": ["import_key", "export_key"],
+            "entry_points": ["import_key"],
             "fallback":     true
         },
         {