Remove __Key field from Backoffice Search if query is not a Guid

[mcl-sz]

When a short search query is used, irrelevant results may arise because the query appears in the Key guide.

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 #16003

Description

When a short search query is used in the Backoffice Search, irrelevant results may arise because the query appears in the Key value.

Before:

After:

[github-actions]

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[Matthew-Wise]

Hey @mcl-sz ! Thank you for your PR to fix #16003 Someone on the core collaborators team will review this soon . Had a quick look at makes sense to me :) Just need to do some testing of course

Thanks
Matt