Remove legacy storage pages removal logic

What does this MR do?

We already stopped deploying to legacy storage. This MR also stop the actual removal of data from this storage.

We still move legacy storage if project gets renamed/moved to another namespace/namespace gets removed.

I think we shouldn't remove this transferring logic, as it would break the migration code. So for now I just created a follow up epic for 15.0 &6703 when can can remove all of this legacy code.

Note that there is a possible bug here:

1. you had 2 legacy pages project first and second
2. when you migrated to 14.* automatic background migration for some reason failed for both of them
3. then you remove first project (note that pages data will still be on disk)
4. and rename second to first

In that case, we'll fail to transfer pages data on legacy storage as first directory already be taken. However this will happen in the background, it will not prevent project from being moved. You'll just get some errors in logs. And if you then run the migration manually, second project will show content of the first.

But it's a very complex case. The only way to reproduce it is to disconnect pages storage for some time until background migration stop retrying... So I think it's ok =)

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

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.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Related to #320775 (closed)