When explaining how to install dependencies for running unit tests,
there are references to "--dev" composer parameter that is the
current default value.
minor #4585 When explaining how to install dependencies for running unit tests, (carlosbuenosvinos)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #4585).

Discussion
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When explaining how to install dependencies for running unit tests,

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | #4584

Commits
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512632e When explaining how to install dependencies for running unit tests, there are references to "--dev" composer parameter that is the current default value.