取消表格导出功能，修复回滚（删表）功能的painc (#1310)

* [feature]:取消表格导出功能

* 修复回滚（删表）painc的问题

* [feature]:修改初始化

server/api/v1/example/enter.go

@@ -3,13 +3,11 @@ package example
 import "github.com/flipped-aurora/gin-vue-admin/server/service"
 
 type ApiGroup struct {
-	ExcelApi
 	CustomerApi
 	FileUploadAndDownloadApi
 }
 
 var (
-	excelService                 = service.ServiceGroupApp.ExampleServiceGroup.ExcelService
 	customerService              = service.ServiceGroupApp.ExampleServiceGroup.CustomerService
 	fileUploadAndDownloadService = service.ServiceGroupApp.ExampleServiceGroup.FileUploadAndDownloadService
 )