change fast uri test threshold to avoid wrong detection

tester/belle_sip_fast_uri_tester.c

@@ -49,7 +49,7 @@ static void perf(void) {
 	t2 = bctbx_get_cur_time_ms() - start;
 	belle_sip_message("t2 = %" PRIu64 "",t2);
 #ifdef __APPLE__ /*antlr3.4 seems much more sensitive to belle_sip_fast_uri_parse optimisation than 3.2, so reserving this test to apple platform where antlr3.2 is unlikely to be found*/
-	BC_ASSERT_GREATER(((float)(t1-t2))/(float)(t1), 0.5, float, "%f");
+	BC_ASSERT_GREATER(((float)(t1-t2))/(float)(t1), 0.4, float, "%f");
 #endif
 }
 static test_t tests[] ={TEST_NO_TAG("perf", perf)};