Removes GitLab Pages legacy storage lease

What does this MR do?

This lease was introduce to guard pages background migraiton from concurrent pages deploy which can change the data

We don't deploy to legacy storage anymore, so we don't need this lease

Changelog: removed

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This change is backwards compatible across updates, or this does not apply.

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I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Edited Sep 01, 2021 by Vladimir Shushlin

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