test/trace_api_test.c: fix gcc error on -Werror=strict-prototypes

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Todd Short <todd.short@me.com>
Reviewed-by: David von Oheimb <david.von.oheimb@siemens.com>
(Merged from #19277)

(cherry picked from commit 1fcd84c)

test/trace_api_test.c

@@ -67,15 +67,15 @@ static int test_trace_categories(void)
 }
 
 #ifndef OPENSSL_NO_TRACE
-static void put_trace_output()
+static void put_trace_output(void)
 {
     OSSL_TRACE_BEGIN(TLS) {
         BIO_printf(trc_out, "Hello World\n");
         BIO_printf(trc_out, "Good Bye Universe\n");
     } OSSL_TRACE_END(TLS);
 }
 
-static int test_trace_channel()
+static int test_trace_channel(void)
 {
     static const char expected[] = "xyz-\nHello World\nGood Bye Universe\n-abc\n";
     static const char expected_len = sizeof(expected) - 1;