Encourage #lease_connection over #connection on AR model #inspect without connection

[joshuay03]

Motivation / Background

Ref: #51349

Seeing as ActiveRecord::Base.connection is soft deprecated, it's probably worth updating this #inspect to encourage the use of one of the suggested alternatives instead.

Detail

Updates #inspect for non-abstract AR model classes to suggest the use of #lease_connection instead of the soft deprecated #connection when the model does not have an established connection.

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Unrelated changes should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.

[ioquatix]

LGTM!