Fix coverity nit in handshake_helper.c

There's no reason to wrap this call in TEST_true() if we're not
checking the return value of TEST_true() -- all of the surrounding
similar calls do not have the macro wrapping them.

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4873)

test/handshake_helper.c

diff --git a/test/handshake_helper.c b/test/handshake_helper.c
index 78eaa01..0add973 100644
--- a/test/handshake_helper.c
+++ b/test/handshake_helper.c
@@ -497,8 +497,8 @@
     case TLSEXT_max_fragment_length_2048:
     case TLSEXT_max_fragment_length_4096:
     case TLSEXT_max_fragment_length_DISABLED:
-        TEST_true(SSL_CTX_set_tlsext_max_fragment_length(
-                        client_ctx, extra->client.max_fragment_len_mode));
+        SSL_CTX_set_tlsext_max_fragment_length(
+              client_ctx, extra->client.max_fragment_len_mode);
         break;
     }