Update project rtc to v3.1.1

libgrabber updated project rtc to v3.1.1.

@rtc-io

### Metadata information

```json
{
  "metadata": {
    "packageManager": "github",
    "name": "rtc",
    "repo": "rtc-io/rtc",
    "files": {
      "basePath": "dist/",
      "include": ["rtc.min.js", "rtc.min.js.map"],
      "exclude": []
    },
    "path": "/home/jsdelivr/files/rtc",
    "localVersions": ["3.0.1", "3.0.2", "3.0.4", "3.1.0"],
    "remoteVersions": ["v2.0.0", "v2.0.1", "v2.0.2", "v2.1.0", "v2.1.1", "v2.1.2", "v2.1.3", "v2.1.4", "v2.1.5", "v2.1.6", "v2.1.7", "v2.1.8", "v3.0.0", "v3.0.1", "v3.0.2", "v3.0.3", "v3.0.4", "v3.1.0", "v3.1.1"],
    "branchVersions": []
  },
  "version": "v3.1.1",
  "updated": true,
  "updatePath": "/home/jsdelivr/files/rtc/3.1.1",
  "branch": "rtc/v3.1.1"
}
```