Don't call generateAlias on #onAliasChange()

[BatJan]

Currently it's not possible to use characters like _ and - in aliases due to this check - At least that is was @nul800sebastiaan told me 😇

Prerequisites

• I have added steps to test this contribution in the description below

If there's an existing issue for this PR then this fixes #20622

Description

Removed the generateAlias() in the alias constant to ensure characters like - and _ can again be used in document type/media type aliases.

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This item has been added to our backlog AB#61214

[github-actions]

Hi there @BatJan, thank you for this contribution! 👍

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[nul800sebastiaan]

Turns out this was already fixed in 17.0.0 but this fix is still good to go for 16.4 in the mean time. Thanks @BatJan!