Replace Hard-coded HTTP Verbs with Constants (#27219)

* Replace hard-coded HTTP verbs with constants in `net/http`

server/channels/api4/import_local.go

@@ -3,6 +3,8 @@
 
 package api4
 
+import "net/http"
+
 func (api *API) InitImportLocal() {
-	api.BaseRoutes.Imports.Handle("", api.APILocal(listImports)).Methods("GET")
+	api.BaseRoutes.Imports.Handle("", api.APILocal(listImports)).Methods(http.MethodGet)
 }