Use FLOAT_TYPE for storage limit

What does this MR do?

Use FLOAT_TYPE for storage limit

INT would not be enough to the cover storage limits we are dealing with since it's send in bytes. It also gets stored as bigint in the database.

We're using FLOAT_TYPE here since BIG_INT is not exposed as a type in our GraphQL lib at this time and it would require us to convert it to a string since INT bigger than 32 bit are not supported: https://spec.graphql.org/June2018/#sec-Int. We also use FLOAT for our other storage size types: https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/graphql/types/root_storage_statistics_type.rb

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