[stable] Make enum function a deprecation, not an error

[ntrel]

The error broke btdu - see: #15405 (comment)

@CyberShadow

[dlang-bot]

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Testing this PR locally

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[dkorpel]

The version should say when to turn it into an error, 10 releases ahead by default, so 2.115

[CyberShadow]

I think @dkorpel meant to change the version in the deprecated tag:

Suggested change

	/* @@@DEPRECATED_2.105.1@@@
	/* @@@DEPRECATED_2.115@@@

[CyberShadow]

Thank you for the quick fix!