Automated submodule update: vrs (#162)

Summary:
This is an automated pull request to update the first-party submodule for [facebookresearch/vrs](https://github.com/facebookresearch/vrs).

New submodule commit: facebookresearch/vrs@4e2af87

Pull Request resolved: #162

Test Plan: Ensure that CI jobs succeed on GitHub before landing.

Reviewed By: georges-berenger

Differential Revision: D70523534

fbshipit-source-id: d2b6d5f5e82ad2a3920879b9c967f8ce1305302e