Fix typo in x509_crt_check() comment

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
diff --git a/tests/suites/test_suite_x509write.function b/tests/suites/test_suite_x509write.function
index abf0a54..485bbe2 100644
--- a/tests/suites/test_suite_x509write.function
+++ b/tests/suites/test_suite_x509write.function
@@ -377,7 +377,7 @@
         goto exit;
 
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
-    // When using PSA crypto, RNG isn't controllable, result length isn'
+    // When using PSA crypto, RNG isn't controllable, result length isn't
     // deterministic over multiple runs, removing a single byte isn't enough to
     // go into the MBEDTLS_ERR_ASN1_BUF_TOO_SMALL error case
     if( issuer_key_type != MBEDTLS_PK_RSA )