修复图片预览bug，移除guava

jodconverter-web/src/main/java/cn/keking/service/impl/OfficeFilePreviewImpl.java

@@ -48,7 +48,6 @@ public class OfficeFilePreviewImpl implements FilePreview {
         boolean isHtml = suffix.equalsIgnoreCase("xls") || suffix.equalsIgnoreCase("xlsx");
         String pdfName = fileName.substring(0, fileName.lastIndexOf(".") + 1) + (isHtml ? "html" : "pdf");
         String outFilePath = FILE_DIR + pdfName;
-        model.addAttribute("switchDisabled", ConfigConstants.getOfficePreviewSwitchDisabled());
         // 判断之前是否已转换过，如果转换过，直接返回，否则执行转换
         if (!fileUtils.listConvertedFiles().containsKey(pdfName) || !ConfigConstants.isCacheEnabled()) {
             String filePath;