MM-52532: Fix golangci warnings for public module (#23918)

https://mattermost.atlassian.net/browse/MM-52532

```release-note
NONE
```

server/public/model/file_info_list.go

@@ -92,7 +92,7 @@ func (o *FileInfoList) SortByCreateAt() {
 
 func (o *FileInfoList) Etag() string {
 	id := "0"
-	var t int64 = 0
+	var t int64
 
 	for _, v := range o.FileInfos {
 		if v.UpdateAt > t {