[artifactory-ha] update nginx TLS config

[dhutty]

PR Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• [x] Chart Version bumped
• [x] CHANGELOG.md updated
• [x] Variables and other changes are documented in the README.md
• [x] Title of the PR starts with chart name (e.g. [artifactory])

What this PR does / why we need it: As discussed with [email protected], this brings the nginx TLS config into line with the "Intermediate" recommendations from https://ssl-config.mozilla.org

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

Special notes for your reviewer:

[eldada]

Artifactory has many other, older clients that use it. Much more than web browsers. Some of these are fairly old, and we try and keep support for a fairly wide range of clients. I'm worried that this change might actually break this. I suggest you wrap this configuration in an if clause with an option to select turning it on or off. I'll also take it internally to see if we can verify this somehow.