bignum_mod_raw.py: Changed the symbol for modular negation to "-".

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
diff --git a/scripts/mbedtls_dev/bignum_mod_raw.py b/scripts/mbedtls_dev/bignum_mod_raw.py
index 34d26f9..c3cb70b 100644
--- a/scripts/mbedtls_dev/bignum_mod_raw.py
+++ b/scripts/mbedtls_dev/bignum_mod_raw.py
@@ -114,7 +114,7 @@
     """ Test cases for mpi_mod_raw_neg(). """
     test_function = "mpi_mod_raw_neg"
     test_name = "Modular negation: "
-    symbol = "(-A)"
+    symbol = "-"
     input_style = "arch_split"
     arity = 1