removed defaults from PHPUnit configuration
minor #11344 remove defaults from PHPUnit configuration (craue)

This PR was merged into the 2.3 branch.

Discussion
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remove defaults from PHPUnit configuration

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

Follow-up to #11329.

Commits
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afc4930 removed defaults from PHPUnit configuration
Merge branch '2.3' into 2.4

* 2.3:
  fixed CS
  [HttpFoundation] Remove content-related headers if content is empty
  removed defaults from PHPUnit configuration