Update project flexgrid to v1.5.1

libgrabber updated project flexgrid to v1.5.1.

@jon4888

### Metadata information

```json
{
  "metadata": {
    "packageManager": "github",
    "name": "flexgrid",
    "repo": "jon4888/flexgrid",
    "files": {
      "basePath": "CDN/",
      "include": ["flexgrid.min.css", "flexgrid.min.js"],
      "exclude": []
    },
    "path": "/home/jsdelivr/files/flexgrid",
    "localVersions": ["1.3.1", "1.4.1"],
    "remoteVersions": ["v1.5.1"],
    "branchVersions": []
  },
  "version": "v1.5.1",
  "updated": true,
  "updatePath": "/home/jsdelivr/files/flexgrid/1.5.1",
  "branch": "flexgrid/v1.5.1"
}
```