Don't use Unicode in .function file

generate_test_code.py doesn't support UTF-8 in .function files (but does
in .data files) when run in a non-UTF-8 locale with Python <=3.6.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/suites/test_suite_psa_crypto_ecp.function b/tests/suites/test_suite_psa_crypto_ecp.function
index 1a7ef3e..5be7a2c 100644
--- a/tests/suites/test_suite_psa_crypto_ecp.function
+++ b/tests/suites/test_suite_psa_crypto_ecp.function
@@ -53,7 +53,7 @@
     }
 
     /* Check masked bits on Curve25519 and Curve448 scalars.
-     * See RFC 7748 §4.1 (we expect the "decoded" form here). */
+     * See RFC 7748 \S4.1 (we expect the "decoded" form here). */
 #if defined(MBEDTLS_PSA_BUILTIN_ECC_MONTGOMERY_255)
     if (family == PSA_ECC_FAMILY_MONTGOMERY && bits == 255) {
         TEST_EQUAL(key[0] & 0xf8, key[0]);