add VPN setup instructions to RM template
This MR adds VPN setup
step to access request template for release managers.
Related issues:
- https://gitlab.com/gitlab-com/infrastructure/issues/2207
- https://gitlab.com/gitlab-org/release-tools/issues/87
And vim auto cleaned two whitespaces at EOLs, @jamedjo please let me know if I need to drop those from MR.