Add dry-inflector dependency

[AliDatadog]

What does this PR do?

This PR adds the dry-inflector dependency to mitigate this error:

❯ bundle exec rake release
rake aborted!
NotImplementedError: Virtus needs dry-inflector gem to constantize namespaced constant names
/Users/user/dd/chef-datadog/tasks/config_specification/models.rb:73:in `<top (required)>'
/Users/user/dd/chef-datadog/tasks/config_specification.rb:23:in `require_relative'
/Users/user/dd/chef-datadog/tasks/config_specification.rb:23:in `<top (required)>'
/Users/user/dd/chef-datadog/tasks/create_integration_monitor.rake:19:in `require_relative'
/Users/user/dd/chef-datadog/tasks/create_integration_monitor.rake:19:in `<top (required)>'
/Users/user/.rbenv/versions/2.7.7/bin/bundle:23:in `load'
/Users/user/.rbenv/versions/2.7.7/bin/bundle:23:in `<main>'

Caused by:
LoadError: cannot load such file -- dry/inflector
/Users/user/dd/chef-datadog/tasks/config_specification/models.rb:73:in `<top (required)>'
/Users/user/dd/chef-datadog/tasks/config_specification.rb:23:in `require_relative'
/Users/user/dd/chef-datadog/tasks/config_specification.rb:23:in `<top (required)>'
/Users/user/dd/chef-datadog/tasks/create_integration_monitor.rake:19:in `require_relative'
/Users/user/dd/chef-datadog/tasks/create_integration_monitor.rake:19:in `<top (required)>'
/Users/user/.rbenv/versions/2.7.7/bin/bundle:23:in `load'
/Users/user/.rbenv/versions/2.7.7/bin/bundle:23:in `<main>'

Fixed by adding dry-inflector in the Gemfile

Motivation

Additional Notes

Possible Drawbacks / Trade-offs

Describe how to test/QA your changes

Reviewer's Checklist