Added a deprecation warning for the command dumper
minor #12627 Added a deprecation warning for the command dumper (Nyholm)

This PR was merged into the 2.7 branch.

Discussion
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Added a deprecation warning for the command dumper

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #12620
| License       | MIT

This fixes #12620

Commits
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07436d7 Added a deprecation warning for the command dumper