Closes #838: Fix the infinite loop of generate missing next-gen images

[Miraeld]

Description

Fix an issue where "Generating missing next-gen files" was stuck in a loop.

Fixes #838

Documentation

User documentation

Webp will be automatically generated on settings save if AVIF is disabled.

Technical documentation

The bail-out avoiding the WebP auto-generation has been deleted.

Type of change

Delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue).

Checklists

Feature validation

• I validated all the Acceptance Criteria. If possible, provide sreenshots or videos.
• I triggered all changed lines of code at least once without new errors/warnings/notices.
• I implemented built-in tests to cover the new/changed code.

Code style

• I wrote self-explanatory code about what it does.
• I wrote comments to explain why it does it.
• I named variables and functions explicitely.
• I protected entry points against unexpected inputs.
• I did not introduce unecessary complexity.
• I listed the introduced external dependencies explicitely on the PR.
• I validated the repo-specific guidelines from CONTRIBUTING.md.

[Mai-Saad]

working as expected (related test https://wpmediaqa.testrail.io/index.php?/cases/view/15282)