Fixes free_namespace_storage_spec to ignore `total limit` text

What does this MR do and why?

Fixes the failing test as reported in #417124 (comment 1460374692). This loosens up the regex expression used to ignore the / 10 GiB portion of the text. This is an intermediary step to fix the failurestale-test while I work on Update `free_namespace_storage_spec` to verify ... (#416569 - closed).

Related: #417124 (comment 1460374692)

How to set up and validate locally

Run bundle exec rspec qa/specs/features/ee/browser_ui/11_fulfillment/utilization/free_namespace_storage_spec.rb against Staging.

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