Fix flakiness in CollectorContextTest (#489)

`testCollectorContextWithKeyword` was failing under [NonDex](https://github.com/TestingResearchIllinois/NonDex) due to implementation-defined ordering of the list of context values.  This PR fixes that flakiness by sorting the list in natural order before inspecting it.

Author: pthariensflame

src/test/java/com/networknt/schema/CollectorContextTest.java

@@ -56,6 +56,7 @@ public void testCollectorContextWithKeyword() throws Exception {
         ValidationResult validationResult = validate("{\"test-property1\":\"sample1\",\"test-property2\":\"sample2\"}");
         Assertions.assertEquals(0, validationResult.getValidationMessages().size());
         List<String> contextValues = (List<String>) validationResult.getCollectorContext().get(SAMPLE_COLLECTOR);
+        contextValues.sort(null);
         Assertions.assertEquals(0, validationResult.getValidationMessages().size());
         Assertions.assertEquals(2, contextValues.size());
         Assertions.assertEquals(contextValues.get(0), "actual_value_added_to_context1");