Fix pages deployment storage migration

What does this MR do?

Fixed #334004 (closed)

See comments on code

Since we ask people to migrate to new architecture in 13.12 and 14.0, this fix should be backported to allow users to follow step in https://docs.gitlab.com/ee/administration/pages/#migrate-gitlab-pages-to-140

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

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Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
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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.

Related to #334004 (closed)