Update schema for excluded urls in DAST site profile form

Related issue - #324163 (closed)

What does this MR do?

Update schema for DAST site profile form's excluded urls field

• GraphQL::STRING_TYPE to [GraphQL::STRING_TYPE] to conform with backend

Screenshots (strongly suggested)

No visual changes

Does this MR meet the acceptance criteria?

Conformity

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• [ x] Separation of EE specific content