Decouple group's storage table from feature flag

What does this MR do and why?

It update's the storage table to show a unified view regardless of additionalRepoStorageByNamespace feature flag.

Previously the component had 2 views: the default one and an extended one that's controlled by a feature flag, now we want the component to have a unified view.

By unifying the view we'll be losing the "excess storage" column, we'll iterate later to add it in a different way.

It also updates the project skeleton loader to have 5 rows instead of 20.

Screenshots or screen recordings

before	after

How to set up and validate locally

1. Navigate to a group (with maintainer+ role)
2. From the left sidebar go to Settings > Usage Quotas > "Storage" tab
3. In the rails console, disable/enable the additionalRepoStorageByNamespace feature flag and observe the storage table doesn't change
   1. Feature.enable(:additionalRepoStorageByNamespace)
   2. Feature.disable(:additionalRepoStorageByNamespace)

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.

Related to #343542 (closed)