fix(appsec): close file item stream after reading content to avoid fd leak

Author: jandro996

dd-java-agent/instrumentation/commons-fileupload-1.5/src/main/java/datadog/trace/instrumentation/commons/fileupload/CommonsFileUploadAppSecModule.java

@@ -133,8 +133,7 @@ static void after(
     }
 
     static String readContent(FileItem fileItem) {
-      try {
-        InputStream is = fileItem.getInputStream();
+      try (InputStream is = fileItem.getInputStream()) {
         byte[] buf = new byte[MAX_FILE_CONTENT_BYTES];
         int total = 0;
         int n;