tests: Make predicate out-of-memory test less aggressive

Currently this test has very large runtime and relies on the fact that
the first memory allocation error causes the test to terminate. This
does not work with new behavior of running the query through and
reporting the error at the end, so make the runtime reasonable but still
generate enough memory to blow past the budget.

tests/test_xpath.cpp

@@ -430,11 +430,11 @@ TEST_XML(xpath_out_of_memory_evaluate_union, "<node><a/><a/><a/><a/><a/><a/><a/>
 	CHECK_ALLOC_FAIL(CHECK(q.evaluate_node_set(doc.child(STR("node"))).empty()));
 }
 
-TEST_XML(xpath_out_of_memory_evaluate_predicate, "<node><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/></node>")
+TEST_XML(xpath_out_of_memory_evaluate_predicate, "<node><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/><a/></node>")
 {
 	test_runner::_memory_fail_threshold = 32768 + 4096 * 2;
 
-	pugi::xpath_query q(STR("//a[//a[//a[//a[//a[//a[//a[//a[//a[//a[//a[//a[//a[//a[true()]]]]]]]]]]]]]]"));
+	pugi::xpath_query q(STR("//a[//a[//a[//a[true()]]]]"));
 
 	CHECK_ALLOC_FAIL(CHECK(q.evaluate_node_set(doc).empty()));
 }