Cleans RemoteId when sanitizing post input from the API (#27049)

* Cleans RemoteId when sanitizing post input from the API

* Fix require check

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/api4/post.go

@@ -55,8 +55,7 @@ func createPost(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// Strip away delete_at if passed
-	post.DeleteAt = 0
+	post.SanitizeInput()
 
 	post.UserId = c.AppContext.Session().UserId