pin chef-vault gem version for continued chef 12 support

[jtschelling]

Description

chef-vault gem release 4.0.1 removed support for ruby version <2.4, because this cookbook still claims that it supports chef versions >= 12.9 this cookbook's gem dependency should be pinned to the latest release that would support chef 12's ruby version

Issues Resolved

N/A

Check List

threw up the PR quick ill check these after this opens. not sure if i need to do the DCO thing, let me know if i do

• [x] All tests pass. See https://github.com/chef-cookbooks/community_cookbook_documentation/blob/master/TESTING.MD
• [x] New functionality includes testing.
• [x] New functionality has been documented in the README if applicable
• [ ] All commits have been signed for the Developer Certificate of Origin. See https://github.com/chef-cookbooks/community_cookbook_documentation/blob/master/CONTRIBUTING.MD

[jtschelling]

https://github.com/chef/chef-vault/commit/585d9329218353f79f967823facb742d0847eeaf

[jtschelling]

oh, my bad. completely overlooked the other PR for this https://github.com/chef-cookbooks/chef-vault/pull/75