Allow using TLSv1.3 with the bundled nginx

Problem to solve

Allows users to use TLSv1.3 to connect to gitlab instances.

Intended users

Admins.

Further details

Making encrypted gitlab connections more secure.

Proposal

I think this requires an updated openssl version as

test@test:etc/gitlab# /opt/gitlab/embedded/bin/openssl version
OpenSSL 1.0.2r  26 Feb 2019

does not support TLSv1.3.

Permissions and Security

Documentation

https://gitlab.com/gitlab-org/omnibus-gitlab/blob/master/files/gitlab-config-template/gitlab.rb.template needs to be adapted.