fix: regognize EUPL as GPL compatible license

[Menrath]

fixes #1262

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Co-authored-by: Menrath <andremenrath@git.wordpress.org>
Co-authored-by: davidperezgar <davidperez@git.wordpress.org>
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[ernilambar]

@Menrath Thanks for the PR. You can take earlier merged PR for adding new license and its related PHP unit tests. #1158

[Menrath]

@ernilambar Thanks for pointing out the other PR, I adjusted this PR accordingly.

[davidperezgar]

Hello, you need to fix the code for the tests...

[Menrath]

@davidperezgar I would need to fix more of the code, first normalizing and then validating is just not safe.

Just EUPL is no guarantee that it is GPL compatible. But EUPL-1.1 or EUPL-1.2 is. But maybe this detail is not that important in this case.

[Menrath]

Tests pass now. But note that a former test changed in c752740

[ernilambar]

Suggested change

	* Plugin Name: Test Plugin with WTFPL License
	* Plugin Name: Test Plugin with EUPL License

[ernilambar]

Suggested change

	* Description: Test plugin for WTFPL license validation.
	* Description: Test plugin for EUPL license validation.

[ernilambar]

This looks unrelated change.