Rename XPath Injection test file

Author: atorralba

java/ql/test/query-tests/security/CWE-643/A.java renamed to java/ql/test/query-tests/security/CWE-643/XPathInjectionTest.java

@@ -24,7 +24,7 @@
 import org.w3c.dom.Document;
 import org.xml.sax.InputSource;
 
-public class A {
+public class XPathInjectionTest {
     private static abstract class XPathImplStub implements XPath {
         public static XPathImplStub getInstance() {
             return null;