[device-status-subscriptions]: remove allOf in sinkcredential

[dfischer-tech]

What type of PR is this?

Add one of the following kinds:

• correction

What this PR does / why we need it:

Removing this allOf.
It was discovered for some code-generator, it will produce unexpected behaviours having the description inside the allOf.

Which issue(s) this PR fixes:

Fixes #225

Changelog input

[device-status-subscriptions]: remove `allOf` in `sinkCredential` in `SubscriptionRequest` component

[bigludo7]

LGTM

[bigludo7]

@akoshunyadi As this is already defined as such in the yaml template for first meta release, this is not an issue to merge this before next MR. But no problem for me to keep it.

[akoshunyadi]

@akoshunyadi As this is already defined as such in the yaml template for first meta release, this is not an issue to merge this before next MR. But no problem for me to keep it.

Yes, the template has it correctly, so it's a kind of bug here. But I wouldn't create a fix for it, just release in Spring25.