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

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

server/channels/api4/shared_channel.go

@@ -11,8 +11,8 @@ import (
 )
 
 func (api *API) InitSharedChannels() {
-	api.BaseRoutes.SharedChannels.Handle("/{team_id:[A-Za-z0-9]+}", api.APISessionRequired(getSharedChannels)).Methods("GET")
-	api.BaseRoutes.SharedChannels.Handle("/remote_info/{remote_id:[A-Za-z0-9]+}", api.APISessionRequired(getRemoteClusterInfo)).Methods("GET")
+	api.BaseRoutes.SharedChannels.Handle("/{team_id:[A-Za-z0-9]+}", api.APISessionRequired(getSharedChannels)).Methods(http.MethodGet)
+	api.BaseRoutes.SharedChannels.Handle("/remote_info/{remote_id:[A-Za-z0-9]+}", api.APISessionRequired(getRemoteClusterInfo)).Methods(http.MethodGet)
 }
 
 func getSharedChannels(c *Context, w http.ResponseWriter, r *http.Request) {