fix: ensure websocket close messages are truncated to 123 bytes (#779)

It's possible for websocket close messages to be too long, which cause
them to silently fail without a proper close message. See error below:

```
2022-03-31 17:08:34.862 [INFO]	(stdlib)	<close_notjs.go:72>	"2022/03/31 17:08:34 websocket: failed to marshal close frame: reason string max is 123 but got \"insert provisioner daemon:Cannot encode []database.ProvisionerType into oid 19098 - []database.ProvisionerType must implement Encoder or be converted to a string\" with length 161"
```

coderd/workspaceresources.go

@@ -108,7 +108,7 @@ func (api *api) workspaceResourceDial(rw http.ResponseWriter, r *http.Request) {
 		Pubsub:    api.Pubsub,
 	})
 	if err != nil {
-		_ = conn.Close(websocket.StatusInternalError, fmt.Sprintf("serve: %s", err))
+		_ = conn.Close(websocket.StatusInternalError, httpapi.WebsocketCloseSprintf("serve: %s", err))
 		return
 	}
 }